Hi,
I think that there are a lot of issues that influence gun balancing and availability. Below are some of the issues that need to be taken into consideration before we (as the obviously deciding factor here) talk about these phalic symbols.
1) Easing new players in
Imagine MEA is your first ME experience and you have to choose between at least 14 assault rifles, or even 3 without any idea of what they do. BW has to make it at least somewhat easy for newbies to pick gear that is both relatively efficient and fits their play style without them having to testfire 20 different guns. (I personally would find that absolutely acceptable but for many players, this would be too much of a chore.)
2) Congruency with the setting
We still aren't quite sure what the setting for our PC will be. Will we be in control of the Ark ship/fleet itself? Are we part of the military that (very probably) runs the operation or are we independent entrepreneurs to which exploring this or that corner of space has been outsourced to? From BW interviews it is clear that BW opts for our PC to start out smaller than Shepard. We're not an N7 (that's not "us" in the trailer) and I guess we don't have much of a history of heroism yet. Therefore it stands to reason that storywise it wouldn't make sense that we have access to top-of-the-line gear ala Black Widdow (or Disciple, seriously guys, wasn't that the best shotgun in the game?!)
3) Crafting
Since the gaming industry thinks that everyone and their mom wants a dedicated crafting system in a game, the question is wether this will be a part of the game mechanics or if they leave it in an ME2/3 way with simple upgrades and modding or go with a more open approach, like a cross between the DA:I crafting and a Borderlandish gun spectrum.
4) Fun and flexibility
One thing that hopefully most developers are aware of is that a game should be fun from the very beginng. It has been said in this thread that a player should earn his good guns. While I understand the intention, namely satisfaction from achieving something, it poses several problems. Firstly, no one wants to say "the game gets good 10 hours in". That's not a selling point and I'm pretty sure BW is aware of that. Secondly, the game is designed to be a roleplaying game, including combat. Offering very little variation at the start also limits players' playstyles. On the other hand, it forces the player to adapt to the circumstances - and consequently become a better player, e.g. using improved tactics or more efficient team choices.
5) The team
One issue that hasn't been mentioned here are your team members. This is worth a thread of its own but concerning weapons and the abilities that these support, it will also depend on your tm abilities and firepower. Think of ME2 on insanity with 2 Jacobs as your team.
6) Upgrades
Are guns going to be upgradeable at all and if yes, how? An RPG lives from relevant and meaningful player decisions. The same is true for the combat and gear part of the game. To have a meaingful decision, you need to have options that have pros and cons. E.g. do I equip this armor-piercing mod along with damage increase or do I take a scope. Cost vs. payoff. Upgrading weapons themselves does not offer a meaingful decision. Of course you will do it, because compared to late-game bank accounts, the costs are negligible. The same is true for the generic +10% damage of ME2.
There are, I think, two extremes, when it comes to guns and gun acquisition. Some want more of a classic RPG system, such as DA:O or World of Warcraft (and yes, that's the same system, even if the scope of loot-whoring is totally different ;D). These players consider the system part of the "progression" of the character as a fighter. It's part of the leveling mechanic of the game. And who doesn't like to go into a fight, for the first time wielding Mr.BadassGun BFG9001.
In the other extreme, guns are not part of the leveling system, but rather preference and playstyle refinement. It has already been mentioned that in ME3 MP, players often stick to certain guns more than to others. Often it's the high DPS dealers like the Harrier or the Reegar Carbine. However, a LOT of players use other weapons. E.g. many engineers use the Mantis sniper rifle instead of the much more powerful Black Widdow with its 3-round clip because it suits their playstyle better as cooldown times for the lighter Mantis are much faster. More importantly, thanks to the (in my opinion excellent) weight restriction, players can choose between weapon character builds or power character builds or anything inbetween, again favouring player decision over linear character progression. This would be more along the lines of the Dark Souls equipment. (It has be shown, that you can beat Dark Souls without anything but a wooden log, showing the [immense] skill of the player)
Having said that, the PC becomes better and better over the course of the game. Thus the enemies need to increase in power. How they do that, if by scaled leveling or increased numbers or (just dreaming here) new tactics and abilites, we shall see. From what I understand, in the ME series, it was by leveling up. So if the player lvls up, the enemies lvl up. But do, or should, the guns lvl up as well? If they don't, wouldn't that disadvantage weapon builds?
7) Availability of Mods
Mods are great because they demand meaningful decisions and offer a lot of freedom. If you look at the ME3 MP you get a good idea of how varied players' tastes can be. And I think, not only ME's success but also the "Mod" success of other shooters show that customisable guns will be much more important in MEA (as all game developers "borrow" successful ideas from other devs.)
8) Realism vs gameyness(?)
Since ME tries to create a living galaxy, it stands to reason that much of the combat needs to reflect the setting of the game. We saw this in ME1 with heat build-up instead of ammo. Storywise, it was an interesting idea and it did change up gameplay somewhat. It wasn't as enjoyable as changing clips after having pinned an enemy to the wall with a billion bullets/pellets. And who doesn't know the almost cathartic feeling when your PC ejects the heat clip from his Mantis after a satisfying headshot. Still BW made the wise decision of using "heat clips" as ammo, and not just return to bullets because it would have clashed too much with the Sci-Fi setting. Gameplay fun normally trumps all other considerations, in any AAA title. And understandably so. But this rule is too simple for a story-driven RPG. One thing that, imho, set ME apart from other RPGs was that from the very beginning, the setting had immediate impact on the gameplay. Biotics, the omni-tool(tech powers) and later the omni-blade, -flamethrower, -whip, -flowerdecorationkit all made the actual gameplay feel more like a true sci-fi game. Contrast this to other sci-fi games that may be good in their own right but often have very little actual sci-fi in their actual gameplay.
So basically the Devs have to walk the line between one and the other. And they will ****** some people off, no question. Still, it seems problematic to argue that something (like lvl1 weapons) is unrealistic. Moreover, except for the general level of existing technology in-universe, very little is pre-defined. It could be that the Ark is a perfectly designed ark ship with everything the settler's heart could desire (if so, BW, I want to see robot prostitutes...you know...for the immersion...and stuff...). Or it could be a hastily repurposed life ship for long-range exploration (e.g. to find the target relay of a dormant mass relay) along the lines of the Quarian life ships. Since both extremes could be justified by the ME story, we will just have to wait and see.
9) ME3 Multiplayer
ME3 MP has been surprisingly well supported with a lot of free stuff and tons of characters (kudos to BW for that). However, I don't think EA forwarded the development money out of the goodness of their hearts, even if EA has a reputation for being extremely consumer friendly. I'm pretty sure it was also a test run for expanding and exploring the combat system in play. And it's actually a pretty good one, considering that it is a third person shooter as well as an RPG and it has action but also needs some skill to be really good at. It is acceptable to assume that both EA and BW were eyeing a new series of the franchise even before ME 3 came out, and especially after it came out.
The question is, will BW scrap the combat system in favour of a completely new one or will they use an evolved ME3 system. The MP has expanded the single player combat system significantly (imho) and for me it stands to reason that this was part of the experimentation process with the ME3 combat system. Because if they scrap the old system, all bets are off anyway since none of us knows anything about the replacement. (One good thing though, the Carnifex will be in the game
)