I cant wait for the Lazaridis paper tbh.
Two things I wonder, will we find L283 in Thracian territory?
Will we find E-V13 from LBA to IA around Hungary and Austria.
I think both scenarios should be plausible. And if we do not find them, then for sure some arbitrary division might have been the case, as in your proposed MDTC and EU/CW one.
But yeah, the Lazaridis paper I think, along with the Troy and Bulgaria ones will shake a lot up.
Edit: Also I do believe people are sleeping on J2a. From what I understand this is the best candidate of Myceneans? Could be wrong. But I got a hunch this haplogroup does not receive the attention it deserves.
I think they will have been intermixed since the LBA expansions, along a zone of interaction in particular, largely along the Danube, but being divided at the start of their respective expansions. As for J2a, I do agree, they might be present in the Channelled Ware people pointing to an earlier South -> North movement in the EBA-MBA and there are now a couple of samples with a quite Northern autosomal background. How this will turn in detail is open, but their main problem for the lack of attention is simply that they had no such long term success like E-V13 and J-L283 had in Europe.