The amp itself looks so cool! The tube with the mesh inside is the EF86, here’s kindof a closeup of a Mullard EF86 I have
Personally I would build a new cab. The construction of this cab does not really look nice enough to where paint or tolex will be able to help much. The 1/4” bottom looks warped, kinda loose, and unevenly joined with a butt joint (the least stable joint for this application). It seems like a foolish idea to use 1/4” for the bottom in the first place. It looks like the 1/4” bottom has flexed allowing the 2 piece chassis to get bent up slightly
I think Vox used to make a lot of cabinets out of particle board, so I’m assuming the original was destroyed by water or something and the owner at the time did their best to save the amp
Although of course I know you don’t want to dump more money into the project, I gotta advise getting a new cab. That cab does not appear to be worthy of the amp.