Hybrid, like Peercoin, approach is probably the best bet if you don't want to go 100% PoS. Solves issue 1 and 2 that you brought up.
Satoshi himself was aware of the usages of coin-age, but he left the scene before it was actually implemented. Gavin seems to be coming around now, with all the talk about 51% attacks on the Bitcoin network.
Well, obviously I would agree the hybrid model is the way to go, and Vitalik was interested in it but thought it was beyond the scope of his project
I guess I'll keep hacking away at MC2