by Bakerloo peak extension to Watford
Presumably as an LU timetabler you know exactly why this cannot and will not happen even in the medium term.
Quite aside from the many millions required to reinstate fourth rail to Watford (to modern standards, of course) and any other peripheral enabling works, there simply isn't the rolling stock available. In common with most LU lines the Bakerloo has a very high stock utilisation, but is this compounded by the age of the rolling stock. One further peak hours train was removed from the timetable last year (or was it the year before...?) to allow for the Heavy Overhaul and life extension works at Acton Works, although tightening up of timings allowed this service to be re-instated at the last timetable change by working the remaining fleet harder. All of that adds up.
To run a service to WFJ in the peaks you need to remove Queen's Park shuttles to allow for the extended running times, in turn reducing capacity in the central section where arguably it is needed the most. In turn this would likely need a major peak hours recast, and also a reworking on all of the driving diagrams to meet the existing agreements and parameters. If only it was as simple as extended a train, eh?!
There is a timetable change on the Bakerloo and Overground in the next week or so which I believe has enhancements to the Overground.
The Working Timetable is available on the TfL website for download, the Bakerloo and Overground are combined into one called Bakerloo...
WTT43 takes effect from Sunday 10 December and is available here:
http://content.tfl.gov.uk/wtt-43-bakerloo-10-december-2017.pdf.
This timetable incorporates the following revisions:
All Week
London Overground have improved their late evening services to operate every 20 minutes between Watford Junction and London Euston until close of traffic. In consequence, Bakerloo Line services have been revised after 22.00.
Sundays
Last northbound trains have been revised:
The last northbound London Overground train has been revised to depart London Euston 10 minutes later at 23.57. In consequence, the 23.37 Elephant & Castle to Harrow & Wealdstone Bakerloo Line service has been revised to terminate at Queen’s Park. A new last train connection between these two trains has been introduced at Queen’s Park.
There's no significant uplift to the Overground service, and it definitely doesn't involve the use of the 172s...