Ah so this was your idea? Thank you for that.
That said your list is not right. Kirby for example breaks the red trampoline with his neutral get up for some reason but is immune to the effect. Villager does the same with his get up attack (Although who would do get up attack unless they know it will get them out of this? I mean that whiffed get up attack does get punished).
That's what my chart is for
That is correct, and when they get back they won't have ledge invincibility.
As for setting it up, depends on the character. Against someone like Samus, you can set it up while she bomb jumps, or against Ness while he PK2s.
Definitely not going to have the same usefulness for each character, but even if you only get this to work once in a set, that's a free stock.
EDIT:
Also let's be serious, if this covers neutral get up and roll, then there is a good chance that this will work at least once. Who sees trampoline above their heads and goes "I'll tempt it, let's jump through it and hope for the best!" or tries to attack it?