What if you increased the block reward to 5 ETH?
Why not 200 ETH reward for a few days.
1. When the Difficulty bomb kicks in the POS fork, the rebelfork can increase POW reward to 200 eth per block for a few days. (100 times more profitable)
2. Miners leave the POS fork to mine on the more profitable POW fork, and the block times skyrockets in the POS fork.