The one that definitively changed my mind on it was Oxford (OXF) to Stafford (STA) via Worcester Shrub Hill and Smethwick Galton Bridge. Not an entirely unreasonable route if you want to avoid Birmingham; it's about 14 miles longer than the route taken by the through OXF-STA trains via Coventry.
The mapped routes for OXF-STA are either map RF, or LONDON. Map RF allows travel via Banbury to Leamington Spa, and then various options around the West Midlands to get to Stafford. No option for going via Worcester.
Oxford to London available maps are:
GC (via Bicester & High Wycombe to Marylebone)
LH (via Reading to Paddington)
RB+WX (via Reading to Waterloo)
London to Stafford maps are:
GC+CM (from Marylebone via Coventry & Birmingham)
GC+WS (from Marylebone via Birmingham & Wolverhampton or Coventry & Nuneaton)
RG+RF (from Paddington via Reading & Birmingham)
SF (from Euston direct via West Coast Main Line with deviations via Northampton and various West Midlands lines permitted)
One of the options that comes up if you join all these together without requiring travel via London is LH+GC+CM.
As LH is the London to Hereford map it's possible to trace "the wrong way" back from Oxford to Worcester. You can then change to map GC.
Since 14th June this year map GC has ended at Smethwick Group. However it previously had a link from Smethwick Group to Worcester Group (following the route taken by the occasional Chiltern trains that extend from Birmingham to Kidderminster). You could then trace one link on map GC (again in the "wrong" direction) from Worcester Group to Smethwick Group, then change to map CM for tracing the final leg from Smethwick - Wolverhampton - Stafford.
This it was only on map CM that you were tracing in the direction intended by a map, and the entire route went nowhere near London but could be traced on a to & from London map combination!