That was one of the first things that crossed my mind too when the Tories reached out to them after the GE. I didn't realise they would be quite so dogmatic though, if that's the right term to use.
The problem you have with NI politics is they have no interest in power, resources or self progression, thus you have little or no leverage in negotiation.
Their motivation is ideological and they would happily bring hardship on to every UK household and throw the country under a bus as long as they could suffer the same hardship.
The UK will rue getting into bed with them.
I see many critiquing Mogg for a supposed you turn, what he has actually done is very clever, he has grandstanded on a pro brexit platform, that has become his political identity, with either a GE or Leadership race in the mix very shortly, he’s now youturning to lobby for the moderate vote, all the while using the DUP as a shield knowing full well that they will fire the bullets for him on a hard line stance and hold the matches if a fire needs to be started. Clever politicking.