I agree, there is a magic in solo diving. I’ve found the willingness to accept solo diving is dive-op dependent. This usually depends on culture and history of the local diving area, thus done places are more willing and supportive than others.
For example what I’ve seen in Bonaire is plenty of people diving alone, without access to redundant gas, extra mask or other redundant gear—that’s usually from shore. On a boat if you have redundant gear they don’t seem to care.
I was diving SM and they specifically said while on the boat everyone needs to have a buddy except the SM guy. I’m sure if someone was diving solo with truly redundant gear they would not have cared.
When diving in Guam, even though I was an experienced solo diver with all redundant gear, I was required to show a solo cert before the boat dive-ops would let me dive solo.
So I just took the solo course for the cert card specifically to mitigate that problem.
Interestingly, after I started diving side mount, no one asked for my solo cert, although I dive solo about 70% of the time off the boat.
In Terms of traveling with a pony, I’ve always taken it as a carry on. In open the tank and keep it covered for tsa. I have a problem with tsa about 50% of the time, but a manager always clears it up. When boarding, I almost always encounter a flight attendant that won’t let me on with the open tank. They get a bunch of people talking about it and finally it gets cleared up.
On the diving end, you have to get a VIP to get it filled. One dive op wouldn’t do inspections except when their tech had it scheduled, which in one particular case wasn’t for ten days from when I dropped off the tank so I just bought a new tank for that trip while on island. Then I had two ponies for the rest of that trip.