Let me make sure I understand. You don't want to check luggage which means you will never be taking your own regulator, or bc/backplate(whichever)/ You would rather rent these life critical devices because you won't be able to fit them in your carryon? Have I got that right? Ok, I'm making some assumptions here, such as you want to take something besides you bc, regulator, computer, fins and mask (I can see renting a wetsuit), like clothing and a toothbrush, perhaps a laptop. Nevermind, I can clearly see that I won't understand. Just a helpful thought, you can wear your bc on the plane. That will save you some weight and space. Hope it is a short flight though cuz they are NOT usually comfortable for a long haul.
For me the inconvenience and risk of checked baggage is far less risky that renting life vital gear which may or may not have been properly maintained and or which may or may not fit like a glove. I have used a rented bc and reg twice. Once when I certified (I immediately went out and got everything) and once in Hawaii when I did not want to haul my 50 lb dive bag for one dive. I took my own reg, and mask. The bc was not a good experience. I know where the dump valves are on mine, I can open pockets and get stuff out without even looking and close them again, I can take it off and put it back on blindfolded, I know exactly which pockets into which to insert the different amounts of weight, on and on. You would rather trust your life to rental stuff to avoid checking baggage. Good luck I truly think you might need it in the not so distant future. May good fortune always smile upon you. I mean it. You might be a very efficient packer and get everything you need in carryon luggage. I can't. If you get on a puddle jumper be aware that sometimes your carryon is limited to 7 kilos. Yes, about 17-18 lbs. To pull this one off you will have to be a world class efficient packer.