If you can make it such, that the economic cost of PoW is constant, or even continuously slight increasing, you can have an automatic price regulating mechanism of your currency, that will always avoid it becoming a speculative asset.
We've been over and over PoS vs PoW in the other thread, so I'm not going to bother digging those old arguments up again. But this one about price stability needs some more attention.
You cannot regulate the price of an item without controlling both supply AND demand. Just changing the supply side isn't enough, and there's no way to control the demand side with this proposal.
To be able to do it, you need a market for selling PoW; miners are buying PoW with their electricity costs - if you had a market where you could buy and sell PoW against USD, you could short it and each short would represented a USD pegged value, but this is a nonsensical example because the value of PoW is ephemeral if its used only for minting coins (this is probably something to think about a little more deeply).