Hmm, the G260, the G250 succesor with Micro-adjust? The most storied and copied second stage regulator ever made? Still among the most durable, reliable and highest perfroming second stages? That one? And the Mark 25 Evo to which no other first stage can equal it's open flow rate though somewhat irrelevant due to the flow restriction being the tank valve and the second stage, that G260 which can flow a xxxxx load of air? And the Mark 25 Evo with even more cold water enhancements? That one? Not viable any more!
I have owned and still own numerous piston first stages and despite beach diving the Gulf coast and the ubiquitous quartz sand beaches and rocky areas I have never seen any scouring or damage to a piston first stage, not a Mark 5, Mark 10 or Mark 20. If you really love cold water and enjoy dives in turbid environments, get a Mark 19 then instead and be happy. That is with the G260s as second stages.