I have been using Ikelite housings for many cameras including my Nikon D300 and now my Nikon D500. They are well made and robust. If I ever needed service, the people at Ikelite were very helpful.
There are other housings which are much more pricey but also very well made.
I use AI computer so don't carry a spare SPG hose. I dive the Hogarthian way.
I carry a low-pressure hose and an adaptor I got from DGEX to convert it to an inflator hose. Having a hose failure I am covered.
I don't carry a spare regulator but I test them prior to dive travel.
I don't think there is any doubt that herd immunity by the methods you mentioned will have it's intended results. Better thru immunity acquired via a vaccine than getting infected. The less host available to the virus, the sooner it's numbers will decrease significantly.
Incidentally, I've been in a situation where I had to assist divers who were out of air (regulator malfunction). We easily shared air with a 7 foot hose and it worked well. Smaller standard hose obviously works but I did not feel that I have to do alot of maneuvering to make a safe ascent to...