If I were writing the curriculum, I would make sure that the students had each learned:
- how to draw safely & quickly (with either hand if both hands are functional)
- how to perform a reload (or how to access the backup gun for a NY reload)
- how to shoot the target while the wheelchair was at various angles to it
- how to shoot from various distances and various angles (eg, not just "check all the angles" but "check all the angles at various distances")
We would also discuss, I think, one of the more common forms of attack against people in chairs -- where the criminal simply dumps the intended victim out of the chair at the beginning of the encounter. For that reason, I'd encourage my students to carry on-body rather than in-chair if at all possible, and I'd make sure they'd each had the experience of firing from the ground in various positions.
Hope some of that helps.