Are you using extract? If you are, to be honest I would not worry about it. Just use extract and then the orange/coriander and the wit yeast and you'll be fine.
If you're AG, you're just going to need it. You could get by with unmalted wheat, especially for a wit. It'd be more to style than the white wheat everyone uses.
The flour + rice hulls is an interesting idea. Might make for one hell of a mess. You're going to need a lot of rice hulls.
Do not just use rice.