I am not pro or con on the debate of not being able to disband. I have always found ways to either use or throw away those militia or flags. While I agree that that particular event is annoying (and has been reiterated time and time again) it is far from 'nearly useless' and at times they can be incredibly useful while others they are a major pain in the ***. I don't feel the solution to that is in particular adding 'disband' but the modification of that particular event.

And you can get them to suicide Arryn. Try not putting them by themselves, but in a massive squad of troops you have either shoring up a center or on a cavalry flank. You'll find that they won't break and can be killed quite efficently if you want them to, when put up against and sort of reasonable opponent/province.