Player customisation... i'm not sure, isn't the whole idea of battlefront is to play as a normal soldier on the front lines, not to customise them to how u want them to look, that would also get confusing, especially online.
I second the idea of more promotion names - on BF2 i got to General far to quickly.
More Vehicles, More Battle Grounds - i think thses are a neccessity if BF3 is to be a success.
Buying and selling weapons, not sure about that - isn't that why u have specific classes, otherwise u could have the stealth of a bothan with the weapons of a wookie or whatever.
A few nice ideas though that i like, as for any ideas i have, i'll have to think about it - most have probably already been mentioned somewhere.