I have never seen a undercab compartment that HAS a disposal without a recepticle.
My only concern and others will know much more than I on this area, but if you did hardwire it to the diswasher and if you used the diswasher and the GD at the same time, somthing might blow. Could exceed the capacity if both on. I would choose another line that does not feed the big juice consumers. Know what I mean???