These couple ideas I've had that seem to be a no brainer but aren't in the game yet.
1) A collect all button -- to collect everything from your mines, collectors, and drills. This seems to be a no brainer especially after the last update we got a reload all inferno towers and x-bows plus a rearm all traps. I would think its a matter of time.

2) when you click on a building I would like to see a left and right arrow appear to hop through the same structure. So if I am looking for a lvl 9 archer tower I can just click on any archer tower I see and the arrow when I press it will hop to my next closest archer tower I can see the info button and the level like normal us there could be and arrow on each side.
Simple things but we are in a convienient culture and this would make things more convienient no doubt.