Birmingham (via Kidderminster)/Hereford - Worcester SH (combine) - Gloucester - Swindon - Reading - Redhill - Ashford - Dover
Birmingham - Worcester - {Gloucester - Chepstow}/Hereford (alternating) - Newport - Swansea - Carmarthen (split/make connections for the ends of the brush)
Weymouth - Westbury - Melksham - Swindon - (Didcot west curve) - Oxford - Leamington - Coventry - Nuneaton - Leicester - Peterborough - Cambridge (using HSTs, and with the Peterborough-Cambridge section line speed raised to 125mph, nearly all of it is dead straight after all, because that endless flat bit is soooo boring and seems to take forever to traverse)
Pancreas - Kettering - Corby - Melton - (reinstate the missing bit at the north end of Old Dalby) - Nottingham - Mansfield - Sheffield - Derby - Crewe
London/Oxford to Birmingham NS via Evesham. Hourly service. Change at Worcester SH for Hereford.
Would make life easier for me
Well I was going to suggest starting the Chiltern Kidderminster-London services back at Shrub Hill, so let's combine the ideas:
London to London. Circular service. Paddington - Oxford - Worcester - Kidderminster - BNS - Banbury - Wycombe - Paddington (and the other way round). There used to be one, in the stated direction (not sure whether it turned left or right at Droitwich though, and don't know if there was one the other way too), that departed Worcester SH at 1235, and provided an unusual opportunity for loco haulage (often a Peak) over an otherwise DMU-saturated route. According to Google I'm the only person on the internet who remembers this, which surely can't be right.
Slip coaches
Oh well, if you're allowed to do that, I'm allowed to do this...
...Pils coaches
At the station, you have a separate platform road with sprung trailing points to get back onto the through road, and probably an extra-long block section after the station. Under the floor of the pils coach, as well as the standard slip-coach apparatus, there is an energy storage flywheel connected to a fusee with a few hundred metres of steel cable wound onto it, and an eye on the end of the cable. When it is ready to depart, the pils guard pulls a lever which extends an arm out to one side of the coach, holding the eye up at solebar height in between the tracks, where it engages a hook sticking out from the rear of the main portion of the train as it passes. Initially, the pull on the cable both accelerates the pils coach and spins up the flywheel; once all the cable has been paid out, the flywheel then winds it in again, transferring the flywheel's energy to the coach and winching it up to the back of the main train, where an auto-coupler engages. The fusee ensures that the initial take-up is smooth and that the engagement of the coach with the main train is gentle. There is also a crank handle somewhere so that if something goes wrong and the cable doesn't wind all the way back in on its own, the pils guard can winch it in by hand (rather slowly, but never mind).
The idea is, of course, that the down train spitting off slip coaches at every junction it passes can be balanced by an up train collecting pils coaches on the fly on the way back, thus getting around the unpleasant limitation of a conventional slip coach setup that it only works one way while causing endless faffing around going the other way.