~ Please make a RPG like ME Trilogy.~
- I would like a new trilogy, because on contrary with DA, in ME I really felt like my Shep has a privileged relation with his crew/friends. And at the end, I really felt like they were all my friends too.
Second reason is, the trilogy has a real evolution by episodes, that makes the story more realist I think. It's like seeing our Shepard grow up. 
- I would like this new game being post Shepard era, because I could never forget him. And play someone else while he's fighting Reapers, sounds a bit strange to me.
Plus, I think Mass Effect is about the Galaxy. And this galaxy needs to evolve. I don't really mind if you chose a canon end, because I invented my own end after Catalist scene. ^^ Or if you don't want to chose a canon end, well Red: they can repear relays and stuffs. Blue, Reapers just gone away in a black hole. Green, everyone is organic and synthetic then ok. Everythings is possible in this universe. Please don't restrain your imagination ! 
- If the game takes place in Shepard era, I would like to investigate on dark energy. Because I was wondering since ME2 what it is exactly. And it interests me. But not as a whole game plot. Just like a priority mission.
- I would like there's less humans, not only in the crew, but in the space too. I always though it's strange that in just 30years, there is sooooo many humans in the galaxy. There should be more asaris, turians and salarians instead. Everywhere. And the crew has too many humans LI.... I'm more interest by aliens than humans, because well... I see humans everyday in my real life.
But aliens are more interesting and they have a bigger place in the universe !
- I would like to discover new species and solar systems.
- If you add a new multi game, I wish you add more game modes like Capture, or Battle Royal (imagine allies force had to fight endoctrinated force), Tower deffence etc..... ME3 multi was great, but it was too repetitive. I understand why you didn't add PVP mode. But you can add more game modes even in PVE.
- I would like to use mako as hamerhead (upgraded, pls
). It could depends on world we visit.^^
- Could you please add ME1 exploration with more activities on worlds (like meet more people like mercs, monsters, tourists, ruins, old artefacts etc...) and ME3 ressources research. Both were fun ! ^^
- Please keep the humor in this game too ! Shepard and his friends had a lot of culte dialogues ! ^^ And it makes them more... real! (And Citadel DLC was ..... like a birthday gift for me ! xD)
- I think the way you put different missions types in ME3 was totally perfect. Like action mission, investigate mission, scary mission etc..... I was never bored cause it was always different ! I don't say ME 1 and 2 were repetitive. But ME3 was perfect for that !
- I wish we could walk in the Citadel like in ME1 !
I was really disappointed that Citadel was soooo little in ME 2 and 3... I know it's not your fault, but if you have time to make a bigger Citadel, I'd really enjoy this ! ^^
- In ME3, I liked the way Shepard's friends were moving on the Normandy, to discuss each other. It was more realistic than when they stayed in their corner like statues. ^^
- I wanna moar pets in my captain cabin !!! \o/ Lol ok I'm joking... but just a bit.
But I really enjoyed the way Shepard's cabin was personalized with all those stuffs, toys and .... fishes ! 
- I wish my Revenant will still be there in this new game... *o* This weapon is a real love to me ! It's like my own Jessie ! 
PS : ME3 has the best musics ever ! Keep its music composers please ! Really ! ^^
PS 2 : Even if you ask fan ideas, I think you're the best ME fans here. Then I wish you will follow your own ideas before ours. ME trilogy was the BEST game I ever played in my life. And I played a lot trust me!
I started it when ME1 was released, and I'm still playing it (I just finished ME3 again, and I start a new ME1 game again !
).
~ I'm really sorry about my bad english, but I'm an Orlesian... :'(~