Nothing rocket science about filling high pressure bottles. The biggest issue is having the access to it. If the bottle is built to be refilled in the field then it was designed for people with access to be able to fill it. I deal with high pressure nitrogen everyday and I am fortunate that I have access to it anytime of the day/night/weekend/holiday that I need it. I realize most do not have access. The biggest thing is to refill slowly to keep the heat down, need to make sure the pressure/bottle temp. are at the desgned temp when the bottle is put back into service. ABS uses a different method, I do not know what it is, but it is not as easy as the BCA.
You answered your own question! Not rocket science to you since you know how to do it! Imagine something you have never done before? Are you as knowledgeable about or as fearless about doing it that you don't ask questions or seek out someone who has done it?
It is great you can do this and have access to it, but 99% of the people out there do not. You even stated that you have to fill slow, but actually the best way is to take the temperature of the bottle or freeze it first to minus 20 then fill it and do the temp again, not just say, "hey fill it slow and you'll be alright"! Guarentted most people won't do it right and be sledding around with less psi in their canister.
ABS takes the screw top off, scrubs the bottle, weights it, freezes it to minus 20, fills it to 4600 psi, take temperature, weights it, lets sit for 72 hours to ensure no leaking, then ships it to the shops. I have blown off over 600 canisters and never had one leak, this can't be said for bca or snowpulse.
Get a refilled canister and handle for an abs is as easy as visiting a dealer, just like going into a dealer to refill bca or snowpulse. With ABS you bring your cartridge and handle in and they exchange it with a refilled one right there, there is a $40.00 charge for this. This pays for the bottles to be sent back, refilled and sent back to the shop.
As I have stated many times whatever system you use you should have a back up extra cartridge for snowpulse and bca or handle and canister for abs so if your out on saturday and you accidentally set off your bag you can just replace the cartridge and keep using it, even if it is in your truck, it is an easy trip back as shops are closed sunday/monday in most cases.
These bags are life saving pieces of equipment so each owner of every specific pack should spend the time to know all the important info on what they need to do to check it often.
