Be warned, this is a big read. I like to go into detail when I say or explain something. Feel free to skim 
I play the series on PC and have modded characters. In DA:O I was a Male, Human Noble Mage. My character was gay and romanced Alistair and they became kings of Ferelden. Because of save importing, Awakening and DA2 recognised that my Warden was a: Male, b:Human Nobel c: Mage d:Gay e:Romanced Alistair in an s/s relationship and rules the country together (It was nice seeing Alistair come to meet his king in Awakening dawww :3). Bodahn referred to the marriage in DA2.
So since it seems save importing won't be in DA:I (though I have seen tweets from...however long ago, saying that they were hoping to implement save importing) i'm afraid they won't have the options to recreate my Gay Warden/Alistair pairing using the keep. I only mention this because even though I did it though modding, BECAUSE DA:O, DA:A and DA2 used save importing, it still recognised everything. I'm not sure how aware the Dragon Age team at Bioware is of modding, especially went to comes to same sex romances, but if they are going to go for The Keep only then I really would like FULL control over the options I use to create the save. Don't just lock me into HAVING to pick a female rogue/warrior in order to have married Alistair and become his joint ruler. Let me recreate my gay noble mage who is married to Alistair as the kings of Ferelden. If The Keep method is a bust then I guess i'll just have to cross my nuts that save importing happens. Note: see my post on page 4 to clarify this topic.
As for the engine thing. My character in DA:O and DA2 was a mage Warden/Hawke and I wore many different armours (the DA2 templar armour, Hawke Mage Champion armour, Sebastian's armour and the regalia of weisshaupt etc. for both games) and used a greatswords, staves (Starfang, Parthalan etc again through modding). Since it may be impossible to mod DA:I i'm worried that we'll lose so much custom content, i'm thinking specifically ported armour and weapons which is how I was able to use all those items in both of the games so far.
I guess i'm scared that in trying to ship a beautiful game they will be cutting out user creativity which as been a staple of PC gaming for so many years in Bioware games. My first ever mod was for the first Knights of the Old Republic game and I finally got round to making a DA2 mod.
Now for the sexuality thing. Bioware has depicted every non-straight character so far as being promiscuous, yes Morrigan says that she has had many men however She is perhaps the straight romance (that I can think of) in the series who has had casual sex. As a gay man myself playing these games it comes across as Bioware thinking that all non-straight people just have sex, sex, sex and more sex. I'm not a stereotype and my sexuality isn't something to be fetishised.
Aveline: woman - Does the whole marriage before sex thing.
Merrill: woman - Isn't stated to be promiscuous. Her whole clan hates her and she doesn't exactly seem like a people person.
Alistair: Straight male - Virgin.
Sebastian: Straight male: Chaste.
Anders, Zevran, Fenris, Isabela, Leliana also are promiscuous for differing reason but at the end of the day all of them are non-straight and they are all promiscuous.
I have no issues with anyone who want to engage in casual sex and I think it is good that Bioware are representing those people in their games, but this isn't my true issue. What I do not appreciate that I haven't been represented in any of the games so far in the romances, I like many of my fellow LGBT people are not all sex crazed 24/7 casual sex, sexy sex. I guess this is somewhat of a rant because i'm feeling that Bioware has the mindset at we are all like that, I hope that isn't the case but after so many Bioware games, that's how it feels and that's rather sad. With so many people consuming video games I feel that Bioware is perpetuating a stereotype which is an issue and speaking for myself, as someone who over the years has had people give me the look of being genuinely surprised when i've corrected them in saying that i'm still a virgin because they've assumed I must have had lots of sex based on my sexuality alone (some more of the werido ones which refused to believe me when I tried correcting them). I don't want Bioware to stop making promiscuous characters, I just want them to stop making them ALL that way, especially the men. I ended up romancing Merrill in DA2 out of spite because my only choices where Anders or Fenris
. (though I will admit that she's super cute and sweet with such a nice accent).
Edit/Note/Thing: I don't think anyone so far as misinterpreted what I have said about the sexuality part yet, this is good and I thank all for not doing that since it probably has to highest potential to be a hot topic, again thanks. Still I do what to make this part just a bit more clear for new people who come across this thread so they don't misinterpret. I have no issues with characters like Isabela, Anders, Zevran being in the game, I think their inclusion is a good thing and makes the games more realistic. What my issue is that for a progressive company like Bioware, the idea of a non-straight character not wanting to have casual sex doesn't seem to have crossed their minds. Search 'tvtropes - All Gays Are Promiscuous' to get a better feeling on my issues. I feel non-straight people are being stereotyped and that bothers me as someone who isn't like that.
However I am still looking forward to playing Inquisition and playing as a blood mage, hopefully i'll finally be able to change people's minds on blood magic so they won't kill me. My heart almost stopped when Wynn right in front of Greagoir
and Irving, accused me of using blood magic....which I was. I convinced them I wasn't but I reloaded to see where it would go. I told them I was using blood magic and then Greagoir tried to arrest me. I had to kill Wynn, Irving, Greagoir, the mages, the templars. Never again, it was horrible.