An earlier suggestion was a tunnel from OOC to somewhere south of Wembley
Central. Crossrail would take over the DC lines from there, with the
Bakerloo and Overground services terminating in new platforms on the east
side of Wembley Central station (there's already tracks there).

That makes no sense -- Crossrail needs to be on the slow lines to get to
Tring, not the DC lines, which will also be accommodating the Met to
Watford Junction.

Presumably the earlier suggestion was to terminate at WJ providing a proper metro service from the north west suburbs into Crossrail.

This is a problem with public projects that you start with a perfectly good idea, in this case a fast metro service from the inner home counties, and then every two bit local politician wants a finger in the pie and we get some serious scope creep. Then we get the complaints that its not suitable for the purpose that it wasn't originally designed for and yet more money has to be spent adapting things. (How long before they decide that half the new rolling stock must be reconfigured for long distance use?)