Cygnuses are unavailable.

Simple. Change it from a Signed INT to an Unsigned INT. That one bit doubles the capacity to 4.2B

And then you have the massive potential downfalls of switching to an Unsigned INT, which have been discussed before because I brought up the idea myself in the past.

Short Version: Do you really trust Nexon enough that they won't screw it up some way to make it double back on itself and give people 4.2B mesos instead of 0? At least when it's a signed INT when you go under zero, you get negatives, not UINT_MAX, which would be 4.2B in this situation. It's far too easy to pineapple it up, especially when we're talking about Nexon here.

Considering Nexon seems to be either doing 64-bit variables or something else to be giving bosses more than 2.1B HP, they should probably just implement that for mesos as well. Then again, that might be (just a little) high. Perhaps then just give a hard-coded maximum, instead of a system limited one.