I think, Jim, part of the reluctance lies in this earlier post of mine:

The Soubry proposal for a ranked voting system does not split the leave vote- despite what some claim - but does allow a vote for leave to express the type of Brexit that is preferred.

As anyone who looks into it will confirm, the ranked voting system does not split the vote, if people who wanted leave were in the majority leave would win.

But - and I think this is where the problem for leave lies - the 'deal' Brexiteers would have to be explaining why the 'no deal' was such a bad idea and vice versa, which would end up with both leave groups showing why the other had problems. And those voters for leave who were content with empty 'leave means leave' rhetoric - which may be a minority of those who voted leave, who can say? - would have to take their ideas to a deeper level. Which risks some saying, "you know what? Both leave routes sound bad."