Of course they would. Preston - Manchester hasn't even been finished yet so do you really think Windermere or any other scheme would have been completed releasing stock?
As always, the fault lies completely with the railway but certain people try to deflect blame elsewhere.
With my reference to "bungling", I was thinking more of the failure of the High Output Plant System (the rolling electrification factory) to electrify plain line as quickly and cheaply as promised. This failing may be more apparent in the south: electrification to Cardiff and Bristol was originally to be completed in 2017, with wires then continuing up the Valleys and along to Swansea. I'm not as familiar with original timescales for the northern electrification project, but I'm under the impression that there have been similar delays.
If the electrification projects had worked as well as hoped by NR, then there may not have been as much demand for DMUs, as well as the ability of W&B to use cascaded EMUs on newly electrified track. But they didn't, so alternative plans had to be formed. I think the original timescale for electrification could have seen all the pacers and many 150s displaced by EMUs before 2020, which would have made the job of fleet PRM modifications quite straightforward. But as we know, things didn't work as well as hoped for, and alternative ideas were needed.
I accept that these alternatives should have been sought earlier, but they weren't, and due to delays to the stopgap solution selected (769) we're in the position we are today. I don't mean to say "it's not Cardiff Bay's fault, NR are to blame" , but I am trying to illustrate what may have been the original plan circa 2012-2015, which then couldn't be realised.