Curious - any references for those “rocket turbine” motors, particularly for this application? I’ve not seen that idea before.
You'd have to pay for storage of water and LOX (and making the LOX) so this wouldn't make sense to prolonged usage. On the plus side, using pure LOX means no NOx formation, so you also lose the catalytic NOx destruction system a stationary gas turbine would need to treat its exhaust.
I vaguely recall some people in Germany were looking at something like this but I don't remember any details.