I personally, do not like the upgrade system. People who have played longer has an advantage because they leveled up, unlocked better weapons and upgraded so their game play can be easier and more convenient. Even though all fps games comes down to skill it still gives the person who has played longer a better advantage through improved accuracy upgrades, less recoil, etc.
you should be able to buy weapon upgrades with money and make the tokens only upgrade the survivor because after you buy all the weapons and clones whats left to buy?