It depends. Pinsider Soren has done an excellent job creating some tournament ROMs for System 11 games that have easily exploitable rules. Earthshaker and Taxi are two, and I know he's created some for other games.

There's a ROM hack floating around that greatly expands the ruleset of Firepower, however, it requires the use of a System 7 board.

And there are a fair amount of home ROMs that resolve some bugs or add handy features to newer WPC games, Whitewater has a home ROM that adds some clever light shows and bug fixes, and the TZ home ROM adds a pause function that holds a flipper up to trap a ball so you can go get that hot pocket from the microwave.

Not much in the way of hacked ROMs to change rules on WPC/WPC95. There are some swear ROMs and other small enhancements as mentioned in the previous post. But nothing that addresses wholesale changes to rules. That's why you see things like CCC and BoP 2.0 where the whole CPU is emulated through a standalone computer to achieve this.

The ones I am aware of are for CFTBL which fixes an major points exploit so one can’t use it in a tournament, and an update for Getaway which has some other changes I can’t seem to remember

https://sites.google.com/site/allentownpinball/tournament-rom-mods

(incomplete) clearinghouse list of known rom mods. There are surely others that could be added to that list.

WPC mods are rarer in that the software is much larger requiring bank selection, so you have to be really careful when changing things from one bank to another. There used to be a forum at pinhacks.com concerning this type of stuff but it is defunct.

For instance the TZ dead end shot becoming the jackpot relight is a good idea and would probably be relatively easy to implement - unless the code for the dead end is in a different bank than the code for the left ramp. Then, you have to make sure you are switching banks back and forth properly and that no other code is expecting to be in that bank at that time. A nightmare to debug if it is like this.

There was also a free implementation of WPC that had a sample twilight zone, but IIRC it was completely different/not completed vs. the stock setup.

You could always hack it in hardware and move the switches around