It all comes back to whether or not it's illegal to run a masternode and for nearly all countries, it isn't. Further, unless you are setting your masternode up on a VPS that takes DRK, your anonymity is already compromised. Further, the majority of existing masternodes won't change out their IP addresses so at least half the network would remain "exposed" anyway.
This is on top of the fact that any sort of onion-based routing will increase latency.
I'm most worried about latency. I'm for speed. I think the quality of service should be paramount. If knowing Masternode IP addresses makes the system vulnerable, then that should be addressed. But paranoid thinking that ip addresses will lead to a government seeking masternode owners out and arresting them... well, I just don't see it happening. At least not in the US, I still think we have that much freedom left for a while ;P if they tried to ban crypto-currencies, the reasons they'd have to cite would be a slippery slope indeed.
so um... #1 for me. If we could enforce minimum RAM and CPU power per MN, all the better. IP address sharing wouldn't bother me as long as the RAM and CPU power is up to par for each. I know this isn't possible yet, but it would be great if it could be done