don't see any problem there.
Maybe it would make sense to replace unlimited by an defined number to avoid "Monopo(o)ls".
(don't know how to do in open source SW)
Big pools could become bigger and bigger due to more frequently forging.
This allure (more accounts => more frequently forging) + self gaining...
And in the end, we will have a big pool with all Nxts in it
As I said ...
It was a big pool, now its a big pool, always be a big pool with all NxT in it ;-)
If you zoom out far enough
, every decentral system becomes centralized by it self ;-)