some GREAT news: with the server interface enhancements i've made it should be possible to PoS mine directly from a thin electrum client
Very interesting. Does it centralize the control of POS mining on the server, though?
However, I think of it like the PoW mining pools we have today - with a bunch of electrum servers, you can choose your "PoS pool" (it can be automated) and just trust that it doesn't tell you bullshit (you just validate the chain work and txs of interest, and the standard electrum client already does that).
That would be what worries me. Because of real or perceived advantage to mining in large POW pools, a few big pools are the dominant roles to approve transactions. The wallet server could acquire great powers to approve new POS blocks. That is centralization.
That said, I think for the same reason why POW pools are successful, POS pools will prevail, too. A thin wallet backed up by a POS pool is just natural for the end user. Your idea, if validated, is more attractive than POS pools that requires the user to hand over their coins to the pool.