Though I am not expert in B 737 structure, I know of other types which have had vulnerable fastener holes reworked in place to prevent anticipated cracking based upon experience with that type. Twin Otter wing strut attach structure in the wing is an example. In some cases, a crack or other defect can be allowed to continue in service with inspection. I have approved two aircraft this way. Analysis of the defect showed that the load could be carried in the structure anyway, and inspection for further crack growth was easy. I'm working on such an approval right now on a smaller GA type. In the worst case, allowing the defect to remain in service unrepaired could involve a small gross weight, or maximum landing weight penalty. Part replacement is a great idea, and the best solution, if it is practical, and the replacement parts are available. If not, more lateral thinking may be appropriate.
I was a part of an inspection team for a prepurchase inspection of an Air New Zealand DC-8 30 years ago, which had a crack in a landing gear trunnion. The crack was monitored using a Douglas approved inspection program, and the plane remained in service. Air New Zealand had the replacement part in stock, but it would be a huge task to install it.
I have no idea what Boeing will propose for this defect, and in the present climate, Boeing will have to be very robust in their proposal. But I'm not imagining a wholesale "replace every pickle fork out there" program.