Current NP penalties are about limiting their future rewards. This is insufficient to disincentivise a would-be malicious actor (they have no intention of sticking around after executing an attack).
Staked ICP (ideally max staked) gives NPs a measurable and visible long-term incentive to keep the network healthy (and not attack it for significant short term gain).
I think this is so needed that I would support an increase in node rewards if that’s what it’ll take. There needs to be PoS if this network is ever going to see large scale adoption. Node machines are not really stake.