First, did the baffle's welds let go because of water sloshing in short, crashing waves or because the tank requires some reinforcing to keep it from "oil canning" or bouncing around?

Secondly, is the access hole in a position where you could access the de-baffled welds by "touching" them through it?

The cause of the broken welds seems to me something to look at before you deal with the fix. It's possible the guage of the tank vs. it's confirguration or tie-downs could be an issue.

The stress on the weld "tabs" may have been too much for fixes that you might look at otherwise. If believe that sometimes, the baffles function as tank reinforcement instead "heft" in the wall thickness of the tank itself.