I did a LOT of work like that, with nothing but our legs and seat.
We never made any of our other students.
When I taught our Intermediate riders I would make them do the no stirrup jumping grids, or the no rein grids, but never both.
I also a couple times blind folded them and set up a "chute" with a jump, and had them do it blind-folded. It really makes you aware of your horse and get a real feel for them.
They were really great little riders!