There will be no greater security than just the PoW, there will actually be less.
I believe its easier to hack 2 or 3 pools in order to control a network over PoW (and often 1 pool has more than 50% of it, so a single target to hit) than hacking all the nodes of a network. Pools also run more code than a node so attack surface is greater.
Network can not be controlled "over PoW" by hacking pools, because hashing power is in hands of miners not pools itself. I don't know how a PoS network can be secure and how a PoS based coin can guarantee privacy, because PoS is inherently centralized.
Maybe privacy is not intended for zano?