Please do not add things that make the game easier for jugglers, but are no benefit for people who play the game with a single path as intended.
One idea from another defense game (Desktop Tower Defense) is "boost towers" that do nothing by themselves, but add multiplier to whatever they are touching as you upgrade them.
There should also be a smoother transition between levels. I usually have a decent maze set up by around level 140 (no air units) and have about 50-60k in points. None of the tanks are getting anywhere near the end of the maze. Then the boss comes through fully upgraded pulse towers with hardly a scratch and gets my base.
To that end it would be nice if you could select a tank and know how many hit points it has left. Otherwise when they get toughter it gets harder to see if you are doing any damage since the bar doesn't move much.
