Here's what I wrote in my own thread 19days ago on the same subject...
If MP is added as a separate mode, I would like it to in the vein of ME3's MP but taken to the extreme, more fleshed out, and done correctly. EX)
MAPS:
Maps would be as large as Fire base Hydra, but DAO/ DA2 styled. It would be great if the details of the environments could be on par with Kingdoms of Amalur or Uncharted 3, but DA themed. That's the scope of detail and size the MP maps should be. The environments should have strategic points that Archers, Mages, Warriors and Rogues and take advantage of. Narrow pathways that funnel people for Rogues and warriors, Hills and cliffs for Archers and Mages, flat areas for all out brawls, etc. There should be environmental dangers that are timed, triggered(Via Traps) or random(Via Environmental) and make stages feel alive. Ex) Lava flow, Wild fires and man made ones, river flood, quick sand, pits, traps, Rock Slides while on mountains.
Location: These maps would take place all over Thedas at famous/Key/ Iconic locations
This means, they can be in the wilderness(Forrest), Cities(In a town(Wither high class or low class), in castles, villages, In taverns!), at ports, (Via Docks), Caves( Deep Roads, Ozammar, Wounded Coast...), On a ship (If they add ship battles(It would be a much smaller map) or The Fade (This can have a randomizing element to it. Be it everytime you get on the stage it's different (As in DA2 maps when some room is missing but it's clearly the same location or in intervals the stage changes. Weather it blinks and your somewhere else or the stage has moving parts, etc. This would be the one stage where strategy is thrown out the window.)
Weather: Each stage can have a random Weather particle generator so all maps stay fresh and each time a stage is loaded, the weather is different(But also depends on environment location. Cant have rain and snow in Ozammar...)
While playing MP, you can DM(Death Match) with a team of friends( You and 3 others fight against other teams of Player controlled characters)
Co-Op: You and a team of PC (Or other players) fight against a common enemy. (This will be theme based. This can be, Dark Spawn, Demons, Bandits( Rogues), Mages, Templars, Armys(Mixed batch of all classes), and Bosses( This will consist of golems, Arch Demons, Dragons, Ogers, etc. This can be broken down 1 step further and go by race as well. Ex) Fighting Elves would consist of fighting in the forest or alienages and maybe have stat bonuses for fighting in home territories. Ex) Hit accuracy drops to all that aren't elves while in forest when fighting elves due to camoflauge, Dwarves get bonus to Strength when fighting in Ozammar from feeling one with The Stone, etc.
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Stats: All characters can have stats like ME3's MP where you allocate points into your character
Store: The store can have armor you can buy to add some kind of bonus on top of your stats after you earn enough money. Ex) You as a player can play all modes, with the exception of Bosses Mode, where you are required/ encouraged to buy better armor so you wont die as easy. Armor may give +50 to fire resistance while fighting Dragons, Arch Demons, etc. Armor might give a small regen ability to Health or Mana/ Stanima. Store armor can just add bonus stats or be cosmetic. Unlike ME3, the store will have packs that you can buy that give you what you want. If you want to buy a bundle of potions, just purchase potions. They will just have to streamline the potion system in MP. Ex) Just like ME3's Direction pad that has 4 items, DA3 will also have it. One direction can have Health, Stanima/ Mana, Revives, and a Buffs Potions spot depending on the buff potion you equip.
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If they Add Co-Op to the SP portion of the game, it would be drop in and drop out Co-op that is only available during big fights( Which means your at a certain part of the game and you can choose to play with someone online for the fight or go solo via promp on screen as you reach the part where a major fight comes up.) Thats one way to handle it. Think RE5(Resident Evil 5's co-op, but simpler)
The other way to handle it and would be the most feasable, is Co-Op Offline only. This is in the vein of Tales Of series. You can have a person/s plug in a controller to help you every fight as one of your party members. This means, you make all decisions and control all conversations during the story, but everytime a battle comes up, you can have them take over an AI controlled character. You can also have them run around the map with you in town, etc. This means if you previously needed to pause and make decisions in DAO or DA2, you will no longer need to since they(yr friends) can make split sec decisions you normally would have to make. This would allow Bioware to make an even more unforgiving AI for you to fight with better strategies.
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Personal Note:
This is just my ideas on the subject of MP and Co-op. I felt Co-Op was the best part of ME3. I had no desire to replay the story, but the Co-OP makes me return regularly despite the insane load times. They had a separate team make the co-op which didn't effect the SP. I believe Bioware can have a separate team make the MP and Co-OP of DA3 as well and draw in old and new fans alike. Even though my main concern in th e SP for DA3, I want MP/Co-Op for DA3. I hope there can finally be a MP that isn't a shooter that becomes popular. If Bioware is brave, they can do it. They're even changing up engines and trying something new for DA3!
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Lastly, what is everyone elses ideas to how MP can be implemented?