There's always a risk of bad actors in any market. Hopefully we have learned and not forgotten the california energy crisis and Enron from the early 2000s. There are regulators who work on this though the market bad actors normally get caught a couple years after the fact. As long as the regulators keep catching them it seems likely that we won't have as many cheats.

The energy markets are significantly layered in power contracts that I would think it would be difficult for an energy storage provider to play that much of a position.