Someone is already doing that  

https://bitcointalk.org/index.php?topic=584719.0

However
Here is the problem of PoS .

https://bitcointalk.org/index.php?topic=615843.msg6751334#msg6751334

  which basically means current holders will depend on the goodwill of past holders not to attack or if you want to avoid that dependence you create centralized trust which is something subject to government/bankers attacks by coercing those individuals holding the trust

Even if you exclude the history attack problem which is fatal large stakeholders will never be able to avoid government influence

If you can identify the minters which are clearing the transactions you can ask them to obey all govs regulations and money transmission rules. It is far easier to identify stakeholders than miners

Those are some reasons I am personally against PoS fork of bitcoin proposed in the first link