Yep.
Thinking out loud..
I see a similarity with CASPER's Security Deposit based system.
The virtual rigs are the safety deposits, and in CASPER terminology every 'v-rig' owner is a validator. We can now penalise not only non-participating miners, but also misbehaving miners who mine on multiple chains and try other 'shenanigans'.
Also - small or large coin holders don't have to mine, and the network can still be secure. In a 1 coin POS system, large stake holders HAVE to mine, or the chain will definitely become insecure.
This is the bit I too am unsure of. Whether it makes a 51% attack easier.
You would now not need 51% of the 'Currency', but just 51% of the mining tokens, BUT this could be worth less or MORE than 51% of the currency.
And finally - Someone may own a percentage of the v-rigs, and simply not wish to sell them at 'any' price (perhaps for security reasons). So that no matter how long the system ran, no miner would 'have to' eventually end up scooping up all the coins, which does eventually happen in all the current implementations of POS I have seen. (ie you leave a miner with initial 20% mining power running. At some point in the future, if he doesn't cash out, he will own everything )