You can technically do it with all PoS coins https://poslist.org/
The barrier as far as my smooth brain sees it is the communication between SAFE and said protocol.
Think about the possibilities. SAFE Network PoR now acting as validator nodes to hundreds of billions of dollars worth of market cap PoS systems but again a working system is required. If it takes another two years with the amounts of money and organisation of something like Cardano or ETH 2.0 they’ll just vote and or fork their networks to create something like SAFE for single purpose use and they have the means to do it.
Essentially what they do is they use the ADA currency, as a lottery ticket so that they can just attribute the right to build the new block to these random lottery tickets, instead of mining it and because the ADA owners themselves are probably not as tech savvy and don’t have or want their equipment on 24/7 the pool gets formed, the pool runs the node validator, pools all of the tokens and hence builds blocks. They don’t require heavy resources because of this, if I am correct they are just doing it on regular machines and some of them I am reading are doing it via friggin AWS!!! Hardly decentralised!!! This is an opportunity if I ever saw one!