Won't work. What you're talking about doing is plumbing the drain line back into the feed line - and the feed line is pressurized. If you do what you say, you'll end up pressurizing both the inlet and outlet of the RO
and you won't get any water at all.
If there was a way to do what you want (economically), you can be sure it would be offered already in a preassembled RO
unit. Not saying it's impossible to do what you're talking about, but it'd be very very expensive to get the correct booster pumps, check valves, etc.