1- Better netcode / matchmaking / lag compensation: the 3rd is a major factor for the "handicap/script" threads, if lag compensation doesn't favor you, your team and players will be slower, react badly, bad first touches, etc and it's not handicap, it's just "invisible button lag"
2- No scripting for "drama", single and multiplayer: there are too many systems in-game atm to "generate" "drama" aka aids aka 45, 90 min goals, defender colliding with each other, defenders doing stupid runs to leave someone alone, GK retardation, etc etc. These are in the single player to boost the AI, but they haven't removed them from player vs player, thus influencing the results of games where only player skill should be involved.
3- For the love of god, do something about coin sellers and coin buyers
4- Change the market - instead of being an auction house, make it a store, controlled by EA, with every player in the game. Every player has a fixed price and we can buy and sell them to and from EA. This fixes almost everything (inflation, speculation to generate coins, ridiculous price fixing, etc). I love trading and the webapp, but not at the expense of a broken market. IMO EA wouldn't even lose money, because without speculative trading, the only way to have top players would be to open packs and get lucky or accumulate FIFA coins from actual playing (although top players would be expensive, so that wouldn't be enough)
5- Improve Pack drop rates and maybe card ratios, like the WC xpac - I loved that one.
6- Shorter cutscenes
7- Full kits shown, not just the shirt
8- IF/special cards for Managers (bonus chem boosts, stat % increases, higher contracts, there are various opportunities)
9- took this one from above because it's a great idea: Ability to 'test drive' any card in the game in an enhanced Concept Squads feature. You can use that squad in a single match offline game but you earn NO coins/XP for using those concept squads.
10- OR revamp the Loan system, before the game was released I always thought it was a tab in-game to loan out players, not a one-time thing at game release and a few in the catalogue. This is a huge missed opportunity, let people test cards out regularly. Either use the controlled store for that (see 4) or have weekly loan rotations where every week a pool of some players are available for us to select 2 or 3.
11- Each time you win a tournament online, it should give the same rewards. Like this year's bug, that's the way it should always be
12- Better same-nation FIFA 16 chemistry
13- I'm torn on position changes, because I'm sure people will abuse the crap out of that. So I dunno.
14- Make themed collections/sets with rewards for completionl.