I am working on a personal mod, for the manufacturing of hydrocarbon fuels. IF this were to seem to be a viable mod... would I be allowed publish it, if it modified the fuel used by your vehicles/planes, via the data-updates process, to use my fuels (either additionally or instead)?

You may modify my fuels with an updating mod and you may also modify my vehicles with an updating mod so they ALSO use your fuels
AS LONG
as you can guarantee that there's no errors or major issues that would need work done by me to fix it.

Nope, all issues will all be on me, no problem there. I really do not expect to go public, but eh. Better to check now just in case.
Thank you sir.