How about this, Oda:
Add an NPC to the Novice Training grounds next to Shion.
If you are a 1/1 Novice, this NPC will warp you to an arena map and automatically save you there.
No storage, no kafra, no mail, warp portal and teleport disabled, the works.
This map will have the USRC NPCS: Gears, consumables, free 90/60 and job change (or 85/60 for the applicable classes). The map would also be shut off from the rest of the game. You can only enter as a 1/1 regular novice, and you can never leave.
It will have access of 4 new GvG rooms for USRC practice. You don't need to implement rules such as consumable/class limitations/number limitations - let the players handle this themselves.
Aka, let the Classic USRC practice just happen on the Classic server.
Just be doubly sure that there's no way out.
Mail is disabled on classic right? lmao