For those aircraft whose WEP use was limited by operating instructions/temperatures, you *could* remove the WEP time limitation and instead simulate failure due to high temps, etc. This would have two drawbacks, however.
1 - you would have to initiate some random failure mechanism to simulate this. Engines weren't guaranteed to fail after exceeding their listed limitations for 10 seconds...
2 - the restrictions on cylinder temps, etc., weren't only or even primarily about preventing immediate failure, but also about engine lifetime, etc. Using WEP too much today (or today, yesterday, and last Tuesday) might instead result in poorer engine performance tomorrow, or even engine failure while in cruise next Wednesday. This cannot really be simulated, especially since a most simulated aircraft don't actually manage to last even 5 hours in the air before being destroyed in the main arena (even the 262's famously short lived engines aren't a factor in this). As a result you would likely have to lump the consequences back into the failure rate in #1, resulting in an unrealistically high chance of immediate failure - after all, since WE don't have to make it home or risk death or long term imprisonment, a small or even moderate chance of engine failure to get just one more kill wouldn't be much of a deterrent.
This points out one of the major differences between a simulator and actual combat - operational constraints (manpower, maintenance and supply requirements, etc) are almost entirely absent.
Mike