I think the 230 and 769 debacles, along with the quiet ending of the 379 trial, have given the UK more than enough evidence for why trying to retrofit new traction types onto units that weren't designed for them, is a bad idea.
There are many, many reasons why this course of action is not the perfect one. However, from where I'm sitting, with experience of these long term projects and the sheer costs involved, it does seem like it is a course of action that will work. Perfect, as they say, is too often the enemy of good. I'd love wires up from Tweedbank to Tain; alas, I am confident I will not live to see it. In our world, without limitless funds, this does seem a bit of a bodge, I will agree.
The important part is that the logic behind the plan that we have is sound. This is a plan, that, if carried out to it's fullness and with the continued confidence of those with the purse strings, will result in material benefits.