I've seen the rhtt train pass me everyday for a week and not once seen a class 66! I've seen class 73's though. Please dtg, make it right. With a cherry on top.
Depends on what version of class 73 is used 73/9 uses AAR MU system meaning a possible combination of Class 66 rear Class 73/9 Front 73/1 and Original Electric Mode SR MU System diesel mode Blue Star MU System means two class 73s on electric mode or Class 33/1. Diesel Mode Class 73/1 & Class 73 with Class 20 31 37/5 33 except for 33/1 SR MU System 40 & 45 Blue Star MU system
Here on the east Kent line you will always see a pair of gbrf 73's in dc mode running the rhtt and the track monitoring train, although I've seen it being run with a pair of 37's once. They use the 66's for hauling freight mainly.
BR livery 73? Southern 73? Gatwick Express (Original) 73? Gatwick Express (modern) 73? Plenty of potential - doesn’t need to be specifically GBRf. Just have it with a GSM-R in the cab, TPWS and it’ll be fine.
Dtg could release in what ever livery they wanted, it makes no difference to me. It wouldn't take long for a decent gbrf livery to appear in the custom liveries.