I think the create a capsule feature is a bit confusing itself. People don't know how many mg you can put in a cap. The problem is powders have different consistencies so you can have varying amounts in a cap.
Your idea is very innovative but a bit hard to grasp. It would be easier to allot a person 100grams and they add the amounts they want. Of course 100 grams of some blends will constitute 200 caps while another blend might make 300 caps. Also I would prefer a caps of jsut one singular ingredient. For instance I haven't tried astragalus before so I'm not sure I want ot put it in a blend, nor am I sure of what dose would suit me best. But single ingredient caps aren't very economical and sort of a waste to the service provided so I'm better off buying a prepackaged product from NOw for example. Maybe you could offer bulk powder in leiu of the capping service as you seem to have an extensive selection that a lot of vendors don't offer.