Nope... Wax is fine, and is required if you want to sand it (which is basically the point of fairing compound)... The point of the wax is to rise to the surface of the resin or gelcoat and form an air barrier on the top to let it fully cure (same purpose as PVA). Once the resin is sanded and wiped down with acetone, all the wax is removed and you are left with plain old resin/gelcoat...
The only reason we don't use wax normally is because you would then have to sand/acetone wipe after every single layup which is a huge pain in the butt.
On a side note, i went out tonight and the wax side of the experiment worked perfectly and sanded really well, however, the PVA side, I think I screwed up... I used a cup of warm water and tried to wash off the PVA and it didn't seem to be doing anything... There was still a very green tint to the fairing compound (the pva was green). I think in my brief research, I determined I put the PVA too soon and it absorbed into the resin... it still fully cured but I wasn't able to wash off the PVA and it was extremely gummy to sand...
I think before moving forward, I'm going to do one more experiment with PVA and wait longer. If it works well, i think PVA is going to be my preference to wax because I'm concerned about getting a good cure in areas where the fairing compound might be too thick like on vertical surfaces and the wax may have trouble getting to the surface.
The brushing the PVA on thing kinda stinks tho... I might have to buy a couple of those prevailer sprayer things...