There are numerous downsides to ECAC. First, it's essentially the Ivy League, and is essentially run by the Ivy schools, so QU is really is a secondhand school when it comes to conference decision making. Not to say UConn's a big boy at the HE table, but there's no inner circle of uppity Ivy douchenozzles there. Second, it's really not that good of a league, HE dwarfs it in terms of success and overall pull. The TV contracts are better in HE, recruiting is better, everything is better. It's nicknamed the EZAC for a reason. Third, the ECAC has an awkward schedule in that most teams (Ivys in particular) don't start their season until three or four weeks after everyone else in the country. Why, I have no idea, but it's always been this way, so their schedule is a bit lopsided. He's pretty much reached the ceiling at QU, there's only so many people who do and will follow QU sports, their facilities, while nice, are still quite small, and wouldn't even qualify capacity-wise for HE.
As for why he turned down UMass, everyone and their brother turned down UMass this past summer. The Holy Cross coach turned down UMass. They've got their own set of issues up there that don't really apply to UConn, namely funding, from what I understand. I would say it'd be a tough get for UConn, especially considering it's not a top job by any means, and he may be holding out for something else, but top flight college hockey jobs are few and far between. The big shot programs are out since those generally hire from within, BU, BC, UNH, Minnesota, UND, Wisconsin, Michigan, etc., and most of those coaches have been there for 10+ years and likely aren't going anywhere anytime soon.
The one glaring exception in the east I see here is Maine. It's well known that Tim(may) Whitehead is on his way out up there and that's a somewhat lucrative position at a big time hockey school that he may want. But again, there are also major funding issues up there in terms of contracts, facilities budgets, etc. But it's a name program that doesn't need to be built-up, like at UConn. But even there, many in the Maine circles want them to hire from within the family and go with former captain Jim Montgomery, currently coaching in the USHL, so who knows.
My guess is, in order to get him they'd have to lay out a well-designed plan for how the school is going to back the program from a facilities and recruiting budget standpoint. I don't see the older Canadian recruit thing as an issue at all, many big time eastern schools do this too, BU being one. But there has to be a clear path that the AD has laid out so that he, or whoever is hired, isn't stepping and shooting from the hip in terms of the vision and goals of the program. UConn's in a very unique but awkward position within the college hockey world, as a big name brand athletic school, one of the two or three highest profile athletic programs in the east that plays hockey, but has, historically, one of the worst hockey programs. While QU is certainly a far more advanced program than UConn right now, the ceiling is that much higher at UConn.
Plus, aside from HE being decimated by defections which would only happen as a result of football realignment (BC, ND, etc. leaving for the B1G), QU has a 0% chance of joining HE, and even in that scenario, the quality of the league would be miles below where it is now.