Thank you for the response! I see what you're saying in regards to diminishing XP. I think most RPGs do this, but paper mario likes to work with small numbers, so instead of requiring more XP to level up, they reduced the XP you get from enemies. That hits a snag when you get down to 0 XP...
As a huge fan of the original Paper mario games...
Yeah, I see where you're coming from. Most of the strategy layer came from choosing badges and upgrading partners. (And, perhaps, timing your level-ups so that they refill your health halfway through a 2-part boss fight.) 90% of the time...