Hmm this was more fun than I expected. Although I have to say the end game got too easy and I just stomped every fight without much trouble at all XD.
I think if you make it so that players don't have to click start and end fight every few seconds it could be an interesting idle concept.
Some suggestions for the gameplay that I think would help the game: Right now every time you choose to build a new unit, it immediately stops the current build and you waste the time spent on that unit. It will be good if you have a queuing system that queue up the next unit if the players so choose, else it just keeps building the old unit.