Are you saying that you'd rather take both Tikki Tooki and Taurog's penalty on a Monk than losing your inventory? 0_0
I'm far from an expert on Monks or Gaan-Telet, but it seems like a -50%dmg monk fighting a 5000HP enemy with Weakening is beyond a lost cause...
Honestly, if you find GG on the first floor you can probably desecrate him right then and there. Prepping something like a Sensation Stone... I dunno, I think I get where you're coming from with the Monk (2x regen that can't be affected by God punishments?) but taking down Horatio as a Monk whose damage is even further nerfed (no getting around desecrating either Taurog OR Tikki)...
My feeling is that the Bloodmage's boosted Sanguine potential might be your best bet, though I haven't given this much thought yet. I can't see myself attempting this challenge...
Shouldn't we be trying to beat VGT with a Goatperson instead? XD