I guess that would be a "LOC/DME" app (or a "LOC + DME", at least), altitudes
must be* published in regard of the distance : same-ish as a glide, just a bit less precise...
The core of the problem is the same : no descent below cleared altitude until established AND cleared for the final.
[Jerk mode ON]
Rotors must be VFR flights, no separation has to be provided.
In order to be safe, just let the helos fly lower than DH.
[/Jerk mode OFF] (... where's the button?)
Edit : (*) I have no clue whether these altitude vs distance are actually published or not.