My basic CCR class was helitrox and as far as I know is colloquially called mod1; at least I sure hope so because when I completed the next class everyone called it mod2. The only other CCR I see is hypoxic Trimix which I thought was mod3? Maybe we should call helitrox mod 1.5
Marie is right about some instructors not being willing to skip air dil (which I find very odd). I’ve also encountered several charter operators who made me cite the standards.
As I think back, I literally don’t think I’ve ever used air as dil. Not that I wouldn’t use air, it’s just that at our typical dive sites we use helium. When I get to cave dive I want a higher po2 for my bailuent.
I stand by my answer to the OP’s question that “minimum experience before doing that training” should be AN/DP to helitrox mod1. I think this route ensures you have the necessary OC experience while value and usefulness are maximized.