To do anything more than a visual inspection of the areas of interest, realistically the engine would need to come out and since the bodywork obscures about a quarter of the circumference of the tubes then the bodywork would need to come off too. After that to carry out magnetic particle inspection the coating should be removed or you could miss defect indications, if you went for dye penetrant inspection then the coating would definitely have to be removed, preferably chemically or you would be likely to get false positive and negative results. My own feeling is that the cracks probably propagate rapidly from nothing to easily visible very quickly indeed so if a thorough visual inspection doesn't pick up anything and the new brace is fitted then that should nip things in the bud...assuming of course that the new bolt on brace can restrict the movement sufficiently to sort out the fatigue life. I will take a (not terribly well) educated guess that the little triangular stiffener plates that were added to the chassis design sometime in 2013 have mainly moved the origin of these cracks from the turns of the wishbone bracket welds to the forward turn of the stiffener plate welds.
