Old Smokey, while i appreciate your knowledge and your experience i think you are not 100% correct on this one.
Lets suppose you are conducting a T/O from Dry Runway with Clearway, using Dry Performance Data. Regulations demand that, when factoring in the clearway, that in the accelerate - go case half of the distance from Liftoff to the point where the 35ft Screenheight is reached must be over the runway (sorry for that formulation, i'll try to provide exact references later). So overhead the Departure End of the Runway, you'll have gained 35ft/2 = 17.5ft height. However, this figure will be a tad lower as climb performence increases with increasing speed and will be almost exact 15ft.
Now lets do the Takeoff again on the very same runway, same conditions but now using Wet Performance Data. The Screenheight is reduced to 15ft, however you are not allowed to factor in the clearway (at least with B777 Performance Tools but i'm thinking this is a general requirement) so when you reach your screenheight of 15ft you'll be at the end of your Take-Off Distance Available which is the Departure End of the Runway.
Exactly the same as when using the Dry Performance Figures! And no reduction in safety.
Now suppose you perform a Take-Off on a runway without clearway eg close-in obstacles. Now using Wet compared to Dry leaves you with less height in the same spot (15ft compared to 35ft) however regulations demand that you cross any obstacle by at least 35ft and make no difference between a Wet and a Dry Runway. That means, that when using Wet Data you still have to achieve 35ft over the first obstacle and thus your climb gradient must be better. This fact is being accounted for in the performance calculation and results in more excess thrust when compared to Dry Runway Data.
So again no reduction in safety.
The only thing which Wet Data really improves is your accelerate - stop performance. Should this result in a higher RTOW compared to a RTOW when using Dry Figures, the latter are used.
So in short, there is no reduction in safety when using Wet compared to Dry Performance Data!!
I stand to be corrected however.