I never liked weapon buying. It tips the balance too much -- giving the more skilled players better weapons while Joe Newbie is perminately stuck with the PGP. If you make it too easy to buy better equipment (as it is in some of the HL pball mods I've seen), after round 2 or 3 everyone is using full autos all the time, which is extremely lame.
I've considered having 2 styles of gameplay: arcade and realistic. Arcade would be what we have now -- rediculous physics and item pickups. Realistic would have a set quota per team for equipment and such. You could have captain-defined weapon distributions or the like in matches. Not sure how this would work in pubs. Realistic would also have more realistic physics and maybe the ability to go prone and lean (which are pointless with the current physics).
Another possibility would be sort of a class-based system: The more equipment you have, the slower you move. This probably wouldn't work well because everyone would get the autococker, then just squat somewhere and spray.
Personally I like the arcade feel. Grabbing equipment is half the game. I just wish mappers would design item layouts better. :\