I may be missing some point that you are trying to make PA, but the FAR/EASA certification and operating requirements for dry and wet runway takeoffs are exactly the same (with the caveat that the FAR operating requirements don't explicitly state that the wet runway takeoff weight cannot be greater than the dry runway takeoff weight.
having a close look at Part 25 the emboldened part would seem to be very worrisome, and IIRC wrt to certification there are four or five scenarios for determining wet TO parameters, I wish I could find the original link, but it was an excellent presentation
I wonder the major operational difference in comparing FAR 121 with JAR ops... that perf A stuff seems a lot more comprehensive,...FAR 121 operational requirements do seem very sketchy..and not really much is said...and they seem quite marginal now after seeing how it's done elsewhere
121-189 does not look very promising at all, especially in conjunction with obstacle clearance, the screen height seems arbitrary as any obstacle must be cleared by 35' and V2 must be achieved by 35' feet..so for an 35' obstacle after the clearway the aircraft only has to achieve 70' the 'screen height' and minimum obstacle clearance...I've always looked at that one and said that can't be right-even while looking at the diagram
so, below seems to indicate that on a wet runway your net height above an theoretical 35' obstacle is only 55'along with that excerpt below from FAR 25, regarding V2