No point asking about the feasibility of substituting gas turbines for their boiler power plant then 😬
The technical feasibility of changing the steam turbines for gas turbines is probably easier than the elevator question. The financial feasibility is worse, however.
Technically, you gain in economy, manpower requirements and especially internal volume in the engine room. You lose in needing to add significant air intake and exhaust/cooling and heat recovery exchangers and, in the balance, you are significantly ahead, to be sure. But, financially! Hoo, boy, is it expensive. It could only be done at a major refit and, from a timing perspective, probably should be done when an angled deck was added, it's that level of major change. But the angled decks were added 10-15 years before effective naval gas turbine systems were available.
Still, if you were doing it, you'd need to open up the ship, right down to the keel, pull out boilers, steam turbines and recuperators, install gas turbines, new much larger airways (in and out) and new higher efficiency recuperators. New stacks, rejig the island to manage that, new bunkerage, piping and pumps to manage the lighter crude/kerosene used for naval gas turbines and then reallocate the interior spaces to use the volume you free up from eliminating the boilers and all the steam trunking.
You's still need steam generation capability, though, if you keep the cats. And that may be why the US went from oil fired steam turbines to nuke steam turbines. Simply because they absolutely needed steam, anyway, to run the cats.
If steam cats are retained it simply may not make any sense to delete the boilers. If you switch to pure helo ops or VTOL/ski jump ops, then going to gas turbine may be useful. The Brit Invincible-class carriers are all GT powered and none have ever had a cat.
Thanks again
Pas de probleme, mon ami.