Wondering if it would be a small job to port from Z80 to 8085?
I'd like to see that CPU supported somehow.
I think the Z80 target in SDCC makes heavy use of IX and IY registers. So you would have to adapt the register allocator (which usually is a difficult piece of code). The rest of the backend is probably more straight forward to change.
I doubt anyone is interested in taking up this job for you. Are you planning to do it yourself?
You will also benefit from a 8085 simulator that can run regression tests. I do not know if one exists.