Churchward might/should replace all the Sprinter stock from ~2030 so if GWR had some more 150s available to them, I wouldn't be surprised if they said "yes", just for six years or so.
If I were the Fat Controller I think I'd bring in the 769s on the North Down Line, as they should have been before whatever happened happened.
Worth noting that GWR are going to introduce 2tpd between Bristol and Oxford, so they'll need stock for that
It is interesting that a number of posts see Churchward as a plan for a future fleet, exact dates vary year or two, but 2028-2032 introduction seems to be expectation.
What does seem to be causing less clarity is how to bridge the gap for next 2 years, seem to be plenty of possible hand me downs for 2026-2031 period, but many of these easy solutions eg spare 158s are 20-25 months away.
I can see why everyone keeps coming back to 175s, simply because everything else is 6-25 months away.
So perhaps it is easier to work backwards and assume Churchward replaces stock 2030-31. Then work out what can be used in interim until then. That would mean :
175s would be 30 years old,
150s would be 43-44 years old,
158s would be 40-41 years old,
769s would be 40-44 years old,
165s would be 39-40 years old,
166s would be 38-39 years old,
Castle HSTs (if kept) would be 49-55 years old
and for completeness if any of following used in interim, by 2030-31
168s (ex Chiltern) would be 29-33 years old
221s would be 29-30 years old,
222s would be 26-28 years old
68s and mk5s a lowly 8-9 years old, younger than IETs and 387s
Sort of feels that depending on if you work forwards from what is available today, or backwards as to what can hang on in there until about 2030, either way debating which is least worst,n rather than ideal.