The Windsor line Should be a natural for electrification.
A self contained branchline which connects to the rest of the railway at a station which is already electrified seems a really good candidate
However I wonder whether the thing that holds back the Windsor line’s case is that of what stick to operate it with?
A 165 clearly isn’t ideal but it’s part of a common batch of trains based at Reading, able to get itself along the GWML at fast enough speed when it does need cycling over with the rest of the “pool”, fairly standard stock
Electrification would mean… what? A four coach 387/1, the EMU that runs GWR’s non-intercity services through Slough? Could be, but is this best use of it on a two mile journey (that a DMU is scheduled to take about six minutes for)?
Since the railway seems to generally have taken the view that “things which warrant more than just four coaches are worthy of electrification, things which cannot ever justify four coaches aren’t busy enough generally aren’t going to be priorities to write up “ (a crude summary, but I hope you get the point), we don’t really do many services that only require short EMUs, so there’s not much to offer to a route like the Windsor branch (without going OTT and chucking a four coach 100mph train on it)
There are examples of short EMUs working, of course, the Hove shuttle had single 315s, but it feels significant that we closed routes with short EMUs in South London and replaced them with trams instead
It’d be more suited to something like a 399, but then that’d mean a micro-class, and all the costs that this entails (even if you did the other Thames valley branches - Marlow/ Henley, it’s very inefficient)
I suspect you’ll probably prefer something like the 387, and fair enough, but the cost of allocating one unit a day just to do a total of six miles every hour - it feels a bit wasteful. But then something needs to be done about these lines that feel like Good electrification candidates on paper but we don’t seem to know how to actually do them
(Sorry, this is maybe doing off into a whole new thread, but I hope you get the idea)