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First off, thats hilarious. How do you drop food & booze through the hole? Put a pit at the bottom and dump or something?
Second, why would this solve the not training with weapons problem? Is it that whenever they go to spar with someone who is a wrestler, they put their weapon up and wrestle back, so isolating the weapon-dwarves will cause them to mostly spar with weapons?
Place a 2x1 garbage dump zone on the floor, 1 tile on solid ground, one over the channel you want them to dump things into. They will walk to the solid ground designated as a dump, and then toss whatever is set to be dumped into the channel. This has plenty of uses for moving things around.
Secondly, I assume it will be because the wrestlers will grab the others, and when grabbed a dwarf can only try to break the hold, not attack using his actual weapon. This is the reason why groups of goblin wrestlers can take down unlucky woodcutters and the like outside, 4 of them hold him down so he can't do anything but try to get loose, and the rest beat him up. This can be tested in adventure mode, which seems to use the same combat system(Although slower).
As for just giving the wrestlers a crossbow, that's not a bad idea for the fortress guard, instead of running after a kobold thief or berserk dwarf, they can just shoot them. And even dwarves with a nerve injury(Brain, spine, neck) will train with a crossbow.(Which is also the safest way to train, I've not once seen a marksdwarf get a sparring injury, not counting the one time I dropped the ceiling of the archery range on a group of them by mistake)
The wrestlers problem seems to be because they wrestle away things from their opponent, like how a quickly activated dwarf beating up an elf can manage to somehow pull the elf's thong off and will then keep holding on to it, even long after he's returned to being a civilian.