Just wondering what the future of the current Moorgate-Stevenage (via Welwyn & Hertford) are? For me this seems an excellent set of services to divert onto Crossrail 2/ Crossrail 3, so freeing up capacity on the ECML.
The proposed Welwyn services on the ECML > Thameslink are new. Moorgate will retain the same number of services as now.
Really? That's great news if so (maybe we should just see how the whole thing progresses first ). Thinking it through though the whole idea in the OP may be getting a little bit ahead of itself.
Likely peak inner service spec is 10 off the Hertford Loop to Moorgate, and 6 from WGC, split 2 Moorgate, 2 to KX and 2 through Thameslink. Although this may change depending what the franchise bidders come up with.
However, the London and SE RUS (the most recent official scheme AFAICS) was quite clear on there being 4 tph from WGC to Thameslink, and 2 tph to Moorgate, giving a total of 12 tph into Moorgate with the 10 tph off the Hertford Loop.