Without wishing to put you off, it really no longer owes you anything. And if it was me doing the welding, I wouldn't want to try on a frame held together with glue.
Another suggestion might be a fibreglass "bandage". Think tape, not car filler. I used to know someone that did just such a thing with an e-stay bike and it lasted for ages!
Still, it does seem a lot of work. And you have a source of spares for your new bike. Seems like quite a good deal to me.