They're already been having cracking issues on the -92 transmission beams and surrounding structure, with the current power & gross weight limits. There's currently an Alert Service Bulletin to do a bunch of rework on/around the transmission beams to alleviate stresses in that area, and hopefully allow the airframes to make it to their predicted SLL (15k hrs, IIRC... but don't quote me on that number). Not to mention the long-running main gearbox issue, which, in Sikorsky's defense, may finally be solved (at current power and GW limits).
Add more power and a shit-ton of .mil mission equipment, and Sikorsky will have to scab on a couple hundred extra pounds of aluminum/stainless/titanium just to make the cracks go somewhere other than around the MGB.
Bristow is operating several S-92s in an offshore SAR configuration in the North Sea. Lots of .civ SAR mission equipment, aux tanks, dual hoist, etc. It would be interesting to see how those aircraft are holding up in that environment...