User blog comment:Nynemout42/Why not be able to purchase more hit points?/@comment-4632427-20130710073054

They already let you pay for promoting units - you can buy boosts to double your SP gain rate.

I'm pretty sure I don't want there to be upgrades that can *only* be acquired through spending nanopods, though. Sooner or later, they'd feel compelled to start hitting us with challenges that *require* that upgrade to defeat, and it's bad enough that they're trying to force us to buy Nanopod units all the time as-is.