I’d like to click down multiple upgrades for the same Tower.
Particularly when I start building a new low level item is is annoying to have to log back in every 5 minutes, 15 minutes, half hour, 2 hours, etc… To get my new Bomb Tower up to a reasonable level. I’d like to be able to fill an upgrade queue.
So as long as I have the money, I can click in several upgrades.
You could even make the queue so it doesn’t deduct the money from your treasury until the time it actually starts the next upgrade (and of course that would mean if your gold had all been raided you, it would cancel the next upgrade.) Otherwise people would never have any money in their treasury, and there’d never be any money to take from anyone.