I agree with Dennis here, 67s look 'right' in Waterloo. How I can't explain, but that silver 67 just looks good, suits the locos much, much better than the EWS livery donned on most of the rest of them.
As for sending a 67 on MK3s down the West of England line, now that is an interesting idea! Would solve a good few on-train capacity problems, although fitting the train in the loops and short platforms at some of the stations would prove difficult. It would be a very interesting sight at Axminster! I can picture sitting there awaiting a train into Exeter, not being in a place to look up the line and suddenly see and hear the 67 pulling in from under the bridge. 67029 on ex-VWC MK3s, perhaps a load 6? Might pull in a few basher wanting to do something better than a unit on the line!
Naturally, 50s on it would be much, much nicer, but then so would a HST. I'd settle for a daily, M-F return hauled by a 67! Especially if it was run by 67029 or another 67 in those colours, the EWS livery hauling ex-VWC MK3s doesn't look right.
A dream it is...