This has been tried before; AAMOF it's been tried many, many times. The only companies still in business are the ones making actions with parts that will interchange with originals, a la Ballard, Meacham and others. I don't know the reason, exactly, but I DO know that I've seen probably a dozen different folks begin making high wall actions that used a 'improved' or otherwise-altered design and/or dimensions, and they've all gone under. Every single one.
SDH and others have made many fine rifles using original actions, with no alterations other than the usual FP bushing and action blueprinting. Your gunsmith apparently doesn't have much confidence in himself so it's probably best that you use AGC instead, while you have the chance.
Regards, Joe
