I really cannot make any comment on homebirth or midwives (I ended up with a c/s and was denied a homebirth outright from the beginning lol)
But in reference to your activism/moral question...I understand your confusion! Going with the similar theory to your second point, have you thought that you can attain the IM, so perhaps given that the places for NHSHB are sooo limited, you would serve women in a worse financial situation better to go for the IM (As opposed to worrying you are forcing someone into another disappointing birth experience.)

It seems that either way you aren't guaranteed to get the midwife you will meet and form a rapport with during your pregnancy, and that you actually want as little intervention as possible even from the midwife, so perhaps the activism concerns are really your only concerns iykwim?
I can only see point in supporting an ailing system if your support will truly make a difference, if anyone will even take note of that support, or if that support wont in fact stress that system or deny someone the ability to use it who doesn't have the other option that you have.

Have you considered a completely independent birth at all? Or do you want amidwife (even if it is pot luck)?

Hope that makes sense...alternatively if it is complete rubbish, just ignore me! lol
I just think that if you are truly interested in the activism for HB in Scotland, there are so many other ways to do it other than submitting to an inferior service to prove a point.

Good luck hun!