that sounds like a great plan and a well thought out execution.
Thanks, I really have been thinking on the topic a lot.
the only problem that i've seen with pure POS coins in general is that it is very difficult to move the chain while staking only.
many chains get stalled for weeks or longer because of this.
It's true if most coins get to the exchanges wallets and(or) coin get lack of interest.
another possibility is to try to list the coin at POSWallet very prior to releasing the POS wallet publicly so that the group staking will keep the chain moving as well.
This is is bad idea: it makes POSWallet holding huge amount of coins (I hate the exchanges for the same reason but this is unavoidable evil)
some dev's of hybrid coins continue to mine empty blocks after the pow phase is over the keep the chain moving but as you said, hybrid coins have a risk.
This is not good solution as well: if anyone is allowed to mine an empty block then this opens a lot of possibilities to manipulate the block chain, otherwise if, say, me would generate an empty blocks signed with above mentioned private key then this put the chain under centralized control. From my point of view it is much more correct for a dev to stake than to PoW-mine: the main idea of the PoS is to make the process more energy-efficient.