I've thought about this for some time and eliminating the reward pool on steem makes a lot of sense. I am not sure how that would impact prices as its the main driver to hold steem in the first place as of right now, but perhaps the decrease in new supply would potentially offset this over time?
Making steem simply a base layer with minimal inflation (1%) while letting all the SMT projects take on the POB stuff seems like the best way to go to me overall...
The negatives would be less demand for steem at least initially, and it would likely cement the witnesses in their current spots.. sort of the problem that EOS block producers face...
Overall though I have a feeling that the current setup is not likely to succeed in the long term and I think making this change is probably the right one to make for the long term sustainability of steem.
Eliminating is a much more severe approach as opposed to simply decreasing the inflation of steem that is going into the pool.
However gotta get RC delegation pools time to get up and running AND you need to see how well OTHER reward pools with different SMTs do. Maybe allowing tons of those to exist and trying tons of equations to the system will teach us if there is a system that works really nicely. No need right now to make drastic changes until we allow new system test the waters for a new and better direction to go.