I don't see the lack or not of a Pool A spot as a decision driver for either USM or UMB. Neither would have been expected to compete for the ECAC East AQ this year or next year - they might well have had a shot at winning the MASCAC, but not the ECAC East. If they wanted to move, they would have done it this year to get in on the league from the start. I would see UMB as more likely to switch than USM - as has been noted, USM has a close travel partner in UNE, they've got regional "rivalries" with Bowdoin and Colby. They are too good a fit where they are.
As for Curry and Wentworth, they seem to be upwardly mobile in terms of NC scheduling. Looking at the PWC a comparison between Curry and Manhattanville shows that Curry has a better OWP and Record vs. Ranked teams than Manhattanville does. Results for Wentworth and Manhattanville are similar.
That's very different from LVC's status in the NE. I don't think it was the move to the W that killed LVC, it was a lack of commitment on the part of the administration.