This would be great. Detroit in the same division would be a lot of fun. BOS, TOR, DET, MTL makes for great rivalries. Terrific fanbases, and the bar is set high in this division with DET there.
Also a big fan of divisional playoffs. That's how rivalries are made. The two most entertaining rivalries of the past couple of decades have been: DET-COL (and, by extension, with DAL, and to a lesser extent STL), and MTL-BOS. Those all came about through rivalry.
And, sure, in the late '90s, DET, COL, DAL, STL and NJ probably formed the best 5 in the league. 4 of those 5 came from the West, so it meant each year those 4 would be battling it out. Now, STL was always a step below the others, but they were a decent thorn in the side of DET. It meant that those four clubs would battle it out and would never see each other in the Finals. But this doesn't matter: it ensured high quality, heated hockey from early on in the playoffs. It was beautiful to watch. That only comes with repeated playoff appearances against the same clubs.