It wouldn't generate more rewards but far more blocks. It wouldn't be a good idea.

As Sairon suggested a rouge player could troll miners by delaying the update of his POS and kill their now ophran blocks. Having more adresses could prevent or do such thing. For me it currently makes no sense to POS at the moment so having a few thousand adresses ready if they could be useful for preventing so that is someting I'm currently thinking about.

The problem with that is not so much the miners, it's the lost transactions and trouble this could cause.