if you follow the track 200 after departure off 20, maintaining a 3deg climb gradient minimum to MSA 3100ft (approx 10 miles) then left turn to Rogag in uncontrolled airspace, then you would I believe fulfill any obstacle issues in that direction.
I would not automatically assume that being able to climb an 5.2% (3 degrees) after departure OEI to a gross altitude of MSA meets the requirements of the OPS Rules because many other issues come into play such as in general;
1. The ILS GS crosses the departure end threshold at 50ft. If you are field limited, you will cross that threshold at 35ft dry (15ft below the slope you are using to clear obstacles) and if it is wet you cross the threshold at 15ft a whole 35ft below the surface you are relying on to clear obstacles by guess what - yes 35ft!!
So if the runway is wet and you need it all, the required net climb profile will parallel your surface 35 feet below which means (in theory) that you are bouncing along nicely at the tops of the obstacles!!!!!!
2. You have to both get to a gross altitude of MSA and accelerate to final take-off speed within the climb thrust limit - possible here but other places may not be so kind. You may get up to the MSA but struggle to accelerate to final take-off speed within 30nm from the point on which the MSA is based - which is unlikely to be reference zero.
3. The method you describe could be very restrictive - work back from having to cross the departure end of the runway at 50ft and see where your 15ft wet reference zero is. This is the point that defines the end of your effective TODA in the wet and will be quite restrictive.
To me, the only issue with taking the departure procedure and not either the only SID or a non-standard clearance remainng within controlled airspace to ROGAG is that the flight (a public transport oprtation) will leave the protection of controlled airspace in an area of high military activity - when the airspace has been designed and procedures put in place that do not make that an essential requirement. Therefore such a routing is optional and must only be taken when all the possible safety issues have been mitigated. In other words - Captains decision keeping within the Part A rules. Think of the result of an Airprox with a fast jet while taking the "short-cut".
The airport has covered it's ass in all respects and passed the book to the company / PIC!!
Quite ironic that for many decades public transport flights departing regional airports into the most frequented and bussiest areas of military flying have not had the protection of controlled airspace - because of course the military object to their operations being restricted in any way. - Newcastle, Teesside and now Doncaster spring to mind!
Domcaster's airspace was not designed to facilitate departures to the east. The only option for such flights is to route initially towards the MTMA and then do a 180 to once again fly past the departure aerodrome climbing. Not a good idea for Pilots, Companies, passengers or ATC. Who is it good for?