I suggest changing default behaviour of ChoiceHolder.htmlize so that there is no <br/> tag and radios and checkboxes are surrounded by <label> instead of <span>
Also it might be a good idea to update ScalaDoc for that method, so that it informs, that this is the place to plug in a custom behaviour by changing it in Boot class.

Discussion thread: https://groups.google.com/forum/?pli=1#!topic/liftweb/Ar8EOCaUnbE