Bridleless is a result of good training in a bit.
I can take my bridle off and gallop, haunch turn, rollback, back up - Anything I can do in a bit I can do bridleless, with no practice, because of good training.
i don't recommend people with closed minds read the following, because it's bound to start a debate.
recently i've started experimenting with a means of starting a horse bridleless (bareback, the saddling process would complicate it enough to have it take years possibly, and does a rope around their neck count as a bridle?) and it's going very well so far. not been bucked, and the particular unhandled horse i'm trying it out on hasn't taken a step out of line yet. so far she walks up to greet me when she sees me in the pasture, we can mount, walk around, steer, stop & backup on command with the rope and legs as my aids. the rest will come in time though as those are the prerequisites for pretty much everything other than performance disciplines. she'll be a good bridleless riding horse though. only equipment used is about 5ft of fairly thin polyester rope. puts most "natural" horsemanship to shame IMO (even though it's based on 3 things, something i've been doing for a while that i found out was loosely similar to "join up" by monty roberts for getting the horse accepting of my leadership & happy in my presence, parelli's "friendly game" for mounting and dismounting, and parelli's "porcupine game" for getting her sensitive to the rope aids)
the process is certainly taking it's time. i've been at it with this horse for 1+ hours daily for about a month just doing those 3 things, and i've tried different things regarding it on saddle/halter broke horses for up to 6 months.
it's certainly not practical, more just something i'm doing out of curiosity. and of course i wouldn't recommend even thinking about such a thing unless you know exactly what your doing. it is extremely dangerous and takes very much patience.
i guess it's something that will take a very long time to understand properly if your used to doing things a certain way and with certain equipment, but how do you think the first person who ever encountered a horse did it?