I love customisation in games. Partly why i'm such a huge fan of RSV 2. However, i don't think a system like that would work in BF. If there was going to be customisations, then my ideas would be:
Armor detail colour- Ideally could be used as if to represent a unit, however the real purpose would be for clans and such. I'm talking about a whole colour change, Just small bits, like outlining on shoulder guards etc.
Barrels/Scopes- For different play styles. I.E choose between different zoom lengths for snipers and barrel sizes- Maybe bigger barrel, more damage, less shots or something. Just tweaks like that could add abit of diversity yet still keep the game in tune with its roots.
Dulce et Decorum Est Pro Patria Mori
Let Mercy Come [/center]