Just some thoughts...

That #26 wire is going to be a problem no matter what type antenna you
end up with. For the longer antennas, HF, etc, it's strength is going
to be sort of limiting. It is sort of difficult to see, but it's far
from being invisible. So, if you are in one of 'those' neighborhoods
that don't like 'visible' antennas there is another choice instead of
an invisible antenna. That's using something that is very visible,
but not normally associated with antennas. The first thing that comes
to mind is a flag pole. Certainly 'do-able', and certainly not going
to be 'simple' if it covers more than one 'chunk' of HF. The 'simple'
way of 'curing' that sort of thingy is to throw money at it, to some
ridiculous point. (Wonder how 'they'ed feel about a 'commemorative'
Atlas missile monument in your yard?)

I think you might do some thinking about what's the longest, sort of
straight, 'run' you can manage using the roof ridge and tree. A few
'bends' in that 'straight' run are allowable, sort of. And then
consider various ways of 'loading' that run. One option might be a
'short' but 'long' inverted 'L', a "lazy-L"? Not exactly the best,
has it's own set of 'problems', but if it works, who cares...much.
Having 'been there, done that' at at one time or another, I really
wish you luck.
- 'Doc