I tried to get through the 10 pages of the thread, but gave up. Hopefully, I am not being redundant in my reaction.
Assuming that the decision is made to go all-in on the future:
Loyalty, Shmoyalty.
If the C's get the right value, trade him. I hope -- because I've loved watching him play -- that Pierce goes to a contender (and I think he'd rather play his last years on a contender rather than in a rebuilding project), but the key is getting the right mix of young prospects, draft picks, financial considerations. I'd take the right trade from any team.
I loved the 1st big 3 as much (if not more) than the current big 3, but I guarantee that if a trade of LB, KM, and/or Chief, had resulted in sustained prominence and a couple more championships (rather than the ensuing 20 year drought), we all be thrilled that we made the moves. And the old big 3 would be just as important to Celtic history as they are now (and just as involved with the organization as they are now).