The BTD5 towers very great, although the mortar wasn't particularly useful, and the dartling gun was almost pointless since it followed your mouse. You couldn't effectively have a banana farm and a dartling gun. The monkey apprentice was woefully overpriced for it's power. For this reason I propose the buff or removal of the dartling gun, mortar and wizard towers.

As far as new towers are concerned it would be nice to have a tower specifically for MOAB class bloons - fully upgraded super monkeys or squads of dartling guns still end up overwhelmed when you start getting to the rounds where 20 BFBs arrive at once. So a tower that is fairly expensive but works only on MOAB class bloons would be incredibly useful. 

Also the "map-wide" powers are almost useless in high rounds, when it is mainly MOAB classes. It would be very helfpul to scrap these for a more useful upgrade to the tower.