I had a cometic gasket blow out on mine, pushed coolant and oil into the timing belt area. I had no clue it happened until the belt snapped. It all happened in a longer drive, so no chance to catch the leak.
I used copper spray on it with perfect surfaces. Still failed at 300whp. Later learned that copper spray is causing multiple failures with Cometics newer gaskets. Used a OEM mitsu MLS on that rebuild. ZERO issues since, same head and block. Didn't even surface the head after the failure.
RTV on a head gasket might work, but I would not use it. Too much chance of it squishing into a coolant, oil, or a drain and causing a restriction or small blockage. LS1 heads are nothing like the 4g63. Just because something works elsewhere, does not mean it's a universal fix. I'd be super cautious. Both hobby wise and professionally, I would not do it.
As for reusing a head gasket, that opinion goes hand and hand with my statements about how I can't believe someone will spend 1k-2k for a turbo, but then be super cheap on critical engine components. I've never reused a MLS head gasket for the fear of a POSSIBLE failure. I've reused MLS on exhaust and intake gaskets with no issue, but those see far less stress than the HG.
Composite is the best for sealing, however it lacks the ability to withstand knock. I know lots of people that use composite on higher HP builds with good luck.