My thought was to put the stainless cfc IN the HLT just like a herms coil and run weldless fittings through the pot to connect it. it would take two pumps, but I have that already. I know cfc's aren't as long as regular herms coils, but if you mash in at the right temp, it shouldn't be hard to maintain that temp. Step mashes, and mash outs might take a little longer to get up to temp. If you run it counterflow with the hlt water for herms, then after the boil when the HLT is empty, switch the HLT water input to tap water for chilling and the wort output to your fermenter. You could even fill the HLT with ice and water and have a built in "pre-chiller" as the cfc would be submerged in the ice water. I have cold well water, so I probably wouldn't need it, but I could if I needed to. When done, heat up the ice water for cleaning the boil and mash kettles. Just seemed like an easy way to kill two birds with one stone, but I've never seen it done.
Hey....maybe it's one of those "makes too much sense, so no one's done it" or maybe it's just dumb, so no ones done it.