Taking a stab at interpreting the routing guide, it seems you have a few options, but there also seem to be some reasonable routes that are not allowed (for example travel up the East coast only seems to be allowed if you travel via London or Exeter, not if you travel via Salisbury and Birmingham)
Your origin routing points are Exeter group or Salisbury.
Salisbury offers routing options of LONDON, BW+BE, BW+BE+GK
LONDON means you can take any permitted route from Salisbury to London, then any permitted route from London to Glasgow
BW+BE lets you travel from Salisbury to Birmingham via Bristol, then lets you travel from Birmingham to Glasgow via west coast routes
BW+BE+GK is similar but with a side trip to Kilmarnock.
If you take a LONDON route then from Salisbury to London you have the option of PZ PZ+WX WW WW+BU+WX
PZ takes you via Basingstoke, Reading and the GWML to London
PZ+WX takes you via Basingstoke, Reading, Staines and Clapham Junction to London
WW I think is the regular SWR route from Salisbury to London.
WW+BU+WX seems a bit of a weird one, appears to let you start out on the SWR route, but then trave via Staines and Clapham Junction to London
And from London to Glasgow you have the option of.GC+BE GC+BE+GK GC+WS GC+WS+GK KG KS+EC+EG LM LM+GK LM+IN+GO PG TC WA+EC+EG WA+ER+GY WA+ER+GY+WN
GC+BE lets you travel from London to Birmingham via high wycombe, then west coast routes from Birmingham to Glasgow
GC+BE+GK another side trip to Kilmarnock
GC+WS honestly seems mostly a duplicate of GC+BE, though it does also add options for travel via Coventry instead of Birmingham
GC+WS+GK Kilmarnock side trip again.
KG East coast mainline up to Edinburgh and then across to Glasgow.
KS+EC+EG Broadly similar to KG but seems to give more flexibility in the details, for example it allows travel via Cambridge which CG doesn't.
LM West coast routes to Scotland.
LM+GK the side trip to Kilmarnock rears it's head again.
LM+IN+GO This looks like the west coast route with a side trip to Carstairs.
PG Great western route to Oxford, then up to Birmingham and west coast to Scotland
TC midland main line to Sheffield, then on to Leeds and then over to Hellifield, Then either Lancaster or Carlisle before continuing up the WCML to scotland.
WA+EC+EG Greater Anglia to cambridge then onwards to Edinburgh via the ECML and over to Glasgow
WA+ER+GY Greater Anglia to cambridge then onwards to Leeds up the ECML and then over to Hellifield, Then either Lancaster or Carlisle before continuing up the WCML to scotland.
WA+ER+GY+WN As above with a side trip to Kilmarnock, and maybe some other local routing options in the Glasgow area.
What i'm not sure about is whether you have to use all the maps in a series. In particular map ER extends to London on the ECML, but it never seems to feature as the first map in a series, only as the second map. So i'm not sure if you can use the Settle and Carlisle having started out on an East Coast mainline train from London or if you have to Travel via a Midland mainline or Greater Anglia route if you want to use the Settle and Carlisle.
Exeter group offers MP+CG MP+CG+GK PE PE+GK PY+YG
MP+CG lets you travel up from Exeter towards Manchester along the welsh border (newport, Shrewsbury etc) to Crewe, then up to Wigan or Manchester, then west coast routes to Glasgow.
MP+CG+GK is similar to above but with a side trip to Kilmarnock.
PE takes you up the crosscountry route to Birmingham and then the West coast to Scotland.
PE+GK another option to take a side trip to Kilmarnock
PY+YG takes you up via bristol, birmingham, Sheffield and York (multiple routes allowed between sheffield and york) then up the ECML to Edinburgh and on to Glasgow.
I have not checked for any easements restricting these options.