It is much safer, IMHO, to put a mechanism in place *prior* to the election for the removal of a rogue element of the board. One that has a very public history is Mambo/Joomla.
There is no legal way to enforce this.
True. This is another case (like histories of decisions) where having documented evidence of the intent can smooth a bumpy road. However, it won't necessarily solve the problem.
Remember, we're not actually trusting the people we elect with anything because there is nothing to trust them with. The organisation doesn't exist yet. If it all goes wrong, we don't need them to stand down because there is nothing actually to stand down from, we can just start again. It's only once the chapter exists that there is an issue and once the chapter exists there will be a means by which board members can be removed (well, they can be not re-elected at the next AGM, we could put some kind of vote of no-confidence clause in the articles [or other bylaws] if we decided to, but there isn't one by default). The only situation in which we would have a problem is if the board gets as far as signing an agreement with WMF but doesn't get as far as allowing members to join so they can attend an AGM (yes, this is precisely what happened last time, so it's certainly not impossible, but I think much has been learnt since then).