Co-op Improvements(Cat Thingy's Thoughts)

Pinging
In BTD5 Co-op, I really wanted to tell my partner exactly where to put a tower, so I thought this was something you could do. You could press a certain button(maybe SHIFT) and a marker would pop up that you could only put on the other person's side. It would tell them where to put a tower, and you have to option to do [example key]+[tower hotkey] to ping a placement for a certain tower.

Improved MIB
If you get the x/3 upgrade, (MIB) your partner should be able to place towers in it's radius, with the approval of your partner, taking money from your funds. This could be an improvement, and could be used if you don't want to ping(See above). Another thing that should change in BTD5 in general is to make the any tower able to target inside the MIB's radius, as it is the Monkey Intelligence Bureau.

BTDB Maps
I think it would be really interesting if there were BTD Battles maps used in Co-op mode. It would be like two people having to pop 1/2 bloons(with the exception of MOAB class bloons)and get 1/2 money. Distraction and Summon Whirlwind and all the other "send bloons back" towers should be able to send it all the way back to the other person's map if it went far enough.