Okay. How about this?
The character would do the recovering animation of a normal tech. Like, for example, my main, Marth, does a hand stand and then jumps to his feet.
Just going on the assumption that anything is possible (Just to get the image across), Marth starts to rise up into the air during the start of his tech animation, and when he reaches a certain point in the animation, he'd be switched into his neutral falling jump animation, and at that point, he'd be at his apex and now falling.
You see what I mean? This way, it'd be clear to see when the invicframes end, and to promote balance, through this animation method, you could force a specific height if its agreed upon by supporters, than techjumped heights should be universal.
Because he'd be in his neutral fall animation, it'd be a clear indication of when he gets control and you know you can do something.
I could make a frame by frame example if I had the ability to.