C13-2 cat system is far from "bog-standard" and is even now being replaced in new-build by the Gen Atomics EMALS system. The Mk7 arrester gear is also due to be replaced over the next few years as well. Biggest problem is not the steam plant required, although that's fairly tricky, but the number of bods required to run the C13s and a "steam-trained" set of engineers - currently submariners only. There are reasons the CVN run around with 5000 people on them..........
If PoW is to have EM cats, then best bet is to buy the US EMALS system and have done with it.