Autopilot for Blimp?

Hi there!
I am working on undertaking a pretty decent project in the next year or so:
A solar powered “hyperblimp” that is more or less a full UAV with an autopilot that requires very little to no human intervention once set on it’s course.

I really plan to go all out on it, even so much as coating it with graphene to stop the escape of gas. My intentions are to have it run continuously/semi-continuously without any additional input, though of course it will never leave my sight.

It seems like it’s a rather costly project to undertake, and I am wondering what the best autopilot program would be to start with - from scratch? If so, how hard would that be to develop?

I’ve read elsewhere that perhaps the ardupilot for helicopters would be best to start off with - because, for whatever reason - it seems a blimp and a helicopter have fairly similar control mechanisms. That doesn’t make sense to me but my experience with either is limited.

I was originally thinking a normal airplane ardupilot would be the easiest - after all, both have propellers that propel them forward, and tail fins for up/down and side to side.
Perhaps just a few bits of code could be added/taken out to make a good blimp ardupilot that would allow it to follow a GPS pattern for a while? Such as removing the need for lift/speed and a few other things.

I’ve been working on figuring out how to just make a good envelope and it seems I am getting that figured out - so, fairly soon I’d like to actually start messing around with flying one - but without the software, I don’t see any point or how I could effective progress.

Blimpudino doesn’t sound like it is ideal either, as it seems like it isn’t built for the right kind of autopilot that I’d like, but who knows… I am very new to this, and I realize I’ve got a lot of learning and experience to do, but I’d love some pointers and opinions on the matter.