I would say that the classes in this game are quite balanced. I see people do well with every classes so apart from obvious things like maps, more classes etc. I would also like to see weapon selections, unique to each class. As well as some sort of kill streak rewards, not necessarily the typical MW2 make the better people even more untouchable but something other than juice. This is such a great game but the only complaint being the scoring system removes more from actually winning, if you tell me my kills and deaths then thats all I will care about so paying for bots and turrets is bottom of the list when in comes to in game upgrades. But, like I said, great game with soooo much potential, and an absolute steal as an arcade title.
I'm a little confused with the last part of your post, I think you are saying that buying bots and turrets deducts the money from your overall match winnings? I don't think it works that way, it spends your earned money, but all the money you earned through the match remains accounted for in the end.