: ...even a wild theory as to how it might be
: done?

As a hard-headed woodworker, here's what I would think about doing: modify the hole into a cool shape of your choice. In my case, I'd consider a shape of the state I live in. Then place a nice piece of wood (thin plywood, hardwood, who cares) behind the bulkhead (?) and trace the shape of the hole onto it. Cut the wood a little oversize. Carefully sand to precise fit, insert into the hole, and 'glass in place. This should convert that ugly, gaping hole into a seriously cool detail.

Well heck, you asked for wild theories.

Cheers,
Kurt Maurer