Day 1. I telephone nats for a clearance on the flight-planned route A-B-C, get told "no thanks, send him D-E-F".
Day 2. Flight-planned route A-B-C, requested D-E-F based on Day 1 experience, cleared D-E-F, launched D-E-F.
Subsequent snotto-call from nats "why hasn't he routed A-B-C as per FPL ?".
Can't win.
If D-E-F is acceptable to nats then make it a Flight Plannable route, so that the operator may file it. Otherwise don't suggest it or accept it.
It's called consistency...