"The "enlarged" chamber has me concerned...."

This is the issue and the answers to it will determine which way you can take action to save the bbl or not.

Enlarged where, how much, what caused it, ect. Any damage to the action.

If it's a chamber that';s just enlarged at the base from poor maint habits or maybe attempts to smooth the chamber up a bit with the ever popular grit paper on a split rod, I wouldn't have any problems with a short sleeve insert well fitted in that back portion of the chamber of an 88. Then recut to match the rest of the chamber after the rebore is done.

I wouldn't do a full length chamber liner at all.
You shouldn't have to do a full length chamber liner anyway as long as you are going from 8 to 9mm. The increase at the neck should take care of any problem up in front of the shoulder. Behind that point, a short chamber liner would be OK IMO.