And as Ruud confirmed in his Rail Mag interview, he thinks the rolling stock is ok (clearly dillusional)
How is it not okay?
With a proper refresh and good maintenance, most of the rolling stock GA has (and the next franchisee will inherit) can go on for many more years.
You could buy all-new trains, with the many teething problems that come with it, or you could work with what you have. New wall panels, flooring, seats, toilet facilities and a proper clean (perhaps with upgraded lighting, CCTV, CIS) and job done.
I'd say you could get quite a bit of life out of the 315s, but definitely loads from the 317s and 321s. They're fast enough and the 317/6s show just how good things could be inside if done correctly (but sadly, NatEx didn't look after them so now they're looking as they do. Based on the 365, FCC has since refreshed its fleet and NatEx, well, didn't).
But GA can't just refresh the entire fleet, especially in such a short time. For one, it needs to keep running trains. The Olympics is also coming up, so all trains will be needed.
The only argument is whether GA should have got rid of the 317/7s. Now if they weren't deemed suitable, I wonder if they could have organised a swap with FCC for its 317/1s? Again, you'd still have the problem of getting changes made, but I wonder if the layout would have been more suitable for the GN route - with 2+2 seating preferable to 3+2. If there are more 317/7s than 1s, it might allow FCC to run more 8 or 12-car trains than they do now.
Anyway - that's a big slide off topic - but going back, I think GA has trains that are fine, except for having been left to get messy inside. Cleaning them up is always going to be quicker than ordering a new fleet though, wouldn't you agree?
In any case, do you really think the DfT would authorise brand new trains when the existing ones are still perfectly usable for now?