Good luck with the rescue, Conn-H. I'm sure it can be saved. From my memory you had two issues with the bore; as long as those are attended to well (and it sounds like they will be), the rest of the job is the same as if no damage had ever occurred at all, given sufficient parts on hand.
You all might have a look at the link Oilyw posted above: http://www.stevecrow.co.uk/projects.htm
To me, the way the touches on the main stack were moved around looks comfy and well-spaced. Those kinds of mods are not that expensive, and can even be done "soft" for a very modest cost, i.e. with epoxy extensions, etc.. What makes Conn Chu stacks clunky, to me, is the way they're weighted. As a general rule, if after your tech gets the tubes/rods nice & clean & smooth, and gets the spring tension optimal for you -- if after that the keys still feel heavy and slow to you, then probably you're one of the people who would much prefer lighter stacks with keys that are designed and weighted differently; if not, then you'll probably be very happy with the original stacks, with just some customizing.
IMO, 6M, Conn Chu alto, Aristocrat (Big B and preceding and directly later models), 10M and 26M/30M models all have stacks that are already plenty fast. When in proper adjustment & optimally goosed (to match player preference, spacingwise), and with optimal spring tension for that player, most people would be happy with how the main stacks are. Low C/Eb and LH table are another question. Even aside from preference, some players actually have health/joint problems that prevent them from using the older American LH pinky tables. IMO, Buescher and Conn low Eb/C tables (putting aside the LH) are very limited in how good they can feel -- it's about how they're weighted. The best situation will be fine (or even great) for some, but not for others.