The pour vial code has been in place for 2 years, and it hasn't generated this kind of discussion the entire time. SUCCESSFULLY subduing someone, and having your buddy pour a vial down their throat, isn't easy. Subdue, in itself, is a tough skill, and you can always escape. Even beyond the escape, you can resist and cough up the contents of the vial and make them waste it.
Personally, I'm all for a lack of 300 kzul berries in someone's skull-chest, and more opportunity for "lesser people" to try and poison others. Since the new brew code came in, I've wanted to do a subdue/kidnap scenario, but it just isn't a fun plotline after about 20 minutes.
I'm with Armaddict here, though, in that if there is potential for abuse, code it differently. If its working as intended, and some people learn the code, its limitations, and apply that knowledge? Sucks, man, but that's no different from the rest of the game. If you have 2 0-day warriors subduing and forcing poison onto people, nothing was stopping them from subduing and attacking you. But now you have more chances to flee, a chance to avoid the damage entirely, and even IF poisoned, there are a number of branching opportunities there, as well.