I was thinking wouldn't it be kinda cool to have a time where the 377s and 423s/421s ran side by side on the brighton mainline our first slam door EMUs in the game and what a route for them to be on
There would also be some 442s as well. (442405 & 442412 At Eastleigh Arlington) (Gatwick Express Services That Operate with 442s about this time or slightly earlier.
Yeah, to me this is a golden era: 319s, slam doors, classic Gatwick Expresses, 455 and 456s, and the first few 377s coming in.
Agreed, this would provide an amazing variety of power that would please a variety of fans. The 319s would be a huge draw for me especially.