this route would be about 70-80 miles long or so. the LNER stops would be Peterborough, Stevenage and of course London kings cross. the great northern stops would be Peterborough, Huntington, St Neots, Sandy, Biggleswade, Arlesey, Hitchin, Stevenage, Knebworth, Hatfield, Welham green, Brookmans park, Potters bar, Hadley wood, New Barnet, Oakleigh park, New Southgate, Finsbury park and London kings cross. this makes for 20 stops and i believe it would be an interesting route, mainly because this is my local line, i do think this route is probably quite a push due to its length and complexity. the LNER trains would be class 800s (9 and 5 car) the great northern trains would be class 717s (i am aware that these companies use other trains but personally they are my fave, i prefer the more modern trains)
i think thameslink uses that and not great northern, but i have no clue you probably know more than me
yeah i’ve made a suggestion on this route before where i go into a lot of detail about it, here’s a link to it if you wanna read it https://forums.dovetailgames.com/threads/ecml-south-london-peterborough-ats.64644/
Not a bad suggestion but in a modern ECML route I would set it 2019 so we can the HSTs along with the 801 (we have more of these than the 800) and the class 700 not 717 as this would mean a large amount of stations wouldn't be used as 717s don't go to Peterborough. Also to keep the Electrostar fans happy the 387s can be used on GN services. Obviously I would prefer it done in the 70s or 80s but there we are. Also to be a bit more exact the route is 76 miles.