This game reminds me greatly of Frantic Frigates (http://www.newgrounds.com/portal/vie w/578155)
The gameplay was good and easy to learn, but there was too little to upgrade. You might want to add more upgradeable stats to the squad members, such as firing speed, attack power, health, regeneration(?).
Also it would be nice if you could select which squad members do appear. Once I bought snipers, my cash flow was reduced drastically because they shoot people from out of sight.
Pause button would also be appreciated and the reset data does absolutely need a confirmation dialog.