In my opinion the most possible scenario is that they were an ancient greek people. Due to geography they had developped a different political system than southern ancient Greeks (but not unique in Hellenic world since Thessalians had a similar political system) and they had more interactions with ancient Balkanic peoples which probably had a cultural impact.
Of course we need proves from archeaology and genetics as you said to be 100% sure. Based on our data we can't reject (neither adopt) the arguments that they were a branch under Graeco-Phrygians separated earlier from southern Greeks.
I agree that it's a pitty there is not an intensive research not only on this issue but also about Dorians, Sea peoples etc.