exept you don't have any real support role in the game... thief as support will be a DPS and Yoshida don't want to have 2 jobs with the same role come out from the same class.
by the way, you can try to say, imagine, imagine, imagine... if the dev don't want to imagine...you can't force them to imagine. we are bound to respect the rule and the will of the dev in a mmorpg.

when they have said, no thief because of lore, because stealing is bad! (and even if you steal bad guys, it's still bad) we are bound to respect this.
steal stats was often showed, i was even in the past say it was a good idea... but the trouble is how balance it? that the difference between imagine and do create a skill and make it work. and here steal stats offer more trouble than any possible skill.

anyway, we are beating a dead horse here... since they have already states, no thief jobs. we must move on and try to see what we can get other than this.