I like a project where anything you do is an improvement. ~my Dad, a long time ago...
I could totally restore that bass, upper horn and all, but at a starting point of more than $2k, just can't see it. It would be a very big job with an awesome result, but cost-wise, no way you'd come out, so we're talking purely a labor-of-love project.
However -and this is a big however- provided this bass still has her Alembic Series electronics, I would totally play what's left of it as-is until such time as restoration was convenient.