Heck, i love this game!

so glad that they're making a trilogy!
but my love for it does not excuse all of its weak points. For ME2, i think:
GAMEPLAY
Adore the gameplay as it is - thats why i've finished it so many times. BUT -
should be multiple routes to get to destination.
More places for specific moves - wallrun-turn-jump, coil, ect.
in 'Mission mode,' be able to meet/talk/interact/control other runners (any one thought about running as Kreeg or Celeste?) Different Runners should have different styles in how they land from a fall, sliding under obsacles (Remember Jacknife from Chapt 2, crouching/running under pipes?) And different offensive patterns.
Free roam - seperate from the story, where you can talk to NPC's, visit shops to buy different clothes (although i like Faith's gear) Explore the city without the CPF trying to kill you. Explore rooftops AND street level to get to grips with different enviroments. The game should show stark contrasts between large crowds and only a few people lingering in lalalalalala or on an office building rooftop.
I agree with the idea of having more NPC's and them reacting to your presence!
STORY
PLEASE! More in-depth plot.
Longer story.
More/different characters.
Tell us more about what hapened to individual characters - we only know what happened to faith! What were Celeste's reasons for doing what she did?
(a lot of questions for characters - cover them there)
What happened to Project Icarus?
What happened to Mayor Calaghan? Was he re-elected?
Did Luitenant Miller die - or was he taken into custody to be used against Faith and Kate?
TRICKS/MORE PARKOUR
I've seen videos on youtube (mainly from Fluidity, the Welsh team) And there is a lot more that could be used. Whether they would help you get from A to B - who knows?
IN-CHAPTER DIALOGUE SCENE
Not fussed on these graphics, but dont know what could be done to improve them, as player needs to stay immersed in the fact that they are going to be attacked, which is lost when the screen turns black preluding a graphics scene.
OUT-CHAPTER DIALOGUE SCENES
I love these scenes! Very rarely is the manga-like style used in anything with a serious/it-could-happen storyline. This is good as it creates a contrast and keeps the player intersted as they are not watching the same graphics all of the time. DICE/EA -

KEEP THE 2D SCENES!!!
CHARACTERS
I'm training to becom a character designer for games, so characters are important to me, so -
I would love to see more information and backstory to different characters; what happened to Kate after Faith left? Why Did Celeste become part of Project Icarus? What were Jacknife's motivations in this? What about the other Runners and Trackers - Kreeg and Drake and all the others? There must be more Runners than the six (estimation) that we have been shown!
What does Kate do now? She could replace Merc as a tracker (she's wanted now and she doesnt know how to run). Or she could proclaim her innocence, and work undercover in the CPF, giving Faith information and tactics used over a secure connection.
What has happened to Celeste? In the chapt 8/9 cutscene, she backs off as Faith shoots at the snipers and explosive barrels. We don't know what happened to her. Its possible that she was hunted by PK units because she knew too much, but she did say "those cops can't move for s**t,' so perhaps she's alive!
Still, i would love to see more Runners and their individual styles.
I assume that Jacknife is dead, and didnt grab the edge of a building like Kate.
Was Mercury buried? Wouldnt it be nice to see Faith visit the grave and talk to him as if he were still alive - it would have sentimental value. Also, how did faith think of Merc? A friend? lalalalalala? A father-figure? Or something deeper? The scene where he died made me question Faith slightly, and it never was clarified how she thought of him, well, not in ME, anyway.
Misc
A 'Mission mode' where you take control of a Runner (or Tracker guiding Runner!) to transport packages and information arround the city. Missions should be given star ratings out of five for 'blue traffic', and 'route dificulty,'. Some missions could be timed. Faith could start these missions by getting her Tracker to 'patch in' another Tracker (eg, Drake) to see if there are any jobs going.
Mission mode should be seperate from story mode, bus some missions should be unlocked after certain story points.
I think that there should be an option to play the game in 3rd person rather than 1st. Sometimes i found the game very disorientating and difficult to judge because of the perspective.
In free roam, i too think that tall buildings or hard-to-find areas should unlock acheviments.
Bring back the Runner Packs! Scatter them throughout the city!
Should be multiplayer options for over internet, split screen AND 'fight against the computer'. I like the idea of Pursuit cops, but i think that it should be a Runner game, where two Runners will play it to see who is better. It could be some kind of mission to beat all of the other Runners!
Semi-destructacble enviroments - some things could break if you hang off of them too long. Gun shots should destroy things too. Not overly keen on gore splattering the ground though.
For online play and/or free roam, you could use faith or a custom designed Runner or a character from the story (Celeste, Kreeg). You could customise their running-styles too!

LOL! I'm talked out! (for now) I'm sure that i'll be adding to this list though! Don't be negative to me - i really do love this game, and i want EA/DICE to make improvements for the next. (And Smeemee, i too have been making and adding to this list for way too long than is healthy! I like your ideas!)
Now, back to Mirror's Edge...