There have been suggestions in the past about having different pools.  It's called segregated reward pools.  Technically, it's all coming from the same pool, but they're segmented and dedicated to different goals.

I think the real solution is to have completely separate areas like "substeems" with their own reward pools and smart contracts.  Smart contracts would allow different rules for each substeem, like how CAPTCHAs are implemented.

I go over the full idea here: 

https://steemit.com/steemit/@inertia/substeem