Just to chip in on this as I'm reasonably well-versed in these issues.
First up, the Croxley Link.
The ideal would be to finish the Metropolitan Railway's plans and extend the branch to Watford Central under the park, then under Clarendon Road up to Watford Junction, and on up the St. Albans branch. Clearly, this would be extremely expensive and disruptive, so it's been ruled out. The next best option is to divert over the old Croxley Green branch to get to Watford Junction as this only requires a new viaduct (alignment-wise, the formation still needs rebuilding to double track). They apparently looked at linking to the St. Albans branch, but have ruled it out on cost grounds. I still believe this would be extremely worthwhile, but in the interests of getting something built, I can accept it for now.
With that diversion in mind, if you want to continue to serve the existing station, you would need to split the service. Watford Met. is 15 minutes walk from Ascot Road, so is quite easy to reach for a large proportion of it's catchment area, and the other side of the catchment area is Cassiobury Park, making it even easy to justify. As a far greater proportion of passengers will want Watford High St./Junction rather than the existing station, the split will likely see something silly like 1 tph serve Watford Met., which just doesn't make sense operationally. Stabling is the elephant in the room though, as LO use Watford Junction's 4 DC line platforms for stabling already...but the Croxley project proposes the same. Should be interesting. Rebuilding Wiggenhall depot is probably out of the question, but there are disused stabling sidings between the WCML and the new lines south of Watford Junction. IIRC they were abandoned due to vandalism though...
Next up, the DC Lines.
The proposal is to remove the DC lines from Euston to a) free up a platform, and b) make the rebuild easier, c) segregate the two lines to improve reliability. Current thinking seems to be to re-extend the Bakerloo from H&W and remove the DC lines service completely, meaning Kilburn High Road and South Hampstead will be abandoned, as Bakerloo trains can turn back at Queens Park, but LO trains can't, they have to reach Willesden Junction's bay for that, and that means shared running.
Personally, I think the best solution is to extend the ELL from H&I to Watford Junction, and cut the Bakerloo back to Queens Park, then to eventually extend the tunnels to Willesden Junction as it's a major interchange.
The only major works required are to widen the Viaduct west of Camden Road for about 20m to remove the pinch point, plain line the track work, then to reinstall the DC equipment on the southern pair of lines...and bingo, fully segregated DC line from Watford Junction to West Croydon, no work whatsoever required west of South Hampstead nor east of H&I, and not using capacity at Euston. HS2's current plans to steal the Primrose Hill link to reach HS1 mean they'll be widening the viaduct to steal the southern lines anyway, so it's clearly possible, and a frequent 12tph metro service is far better use of the lines than a piddily 4 train per day HS2-HS1 link.
To be clear - there's no talk whatsoever of abandoning any stations other than Kilburn High St. or South Hampstead though.
