You're not getting poison magic back on Summoner unless you somehow convince the people who now play the job to want it back. We don't. What we largely want is more abilities for new Summoner, not things from the past. You want dots and poison magic, then please ask for Necromancer or another dark-themed caster which this game is missing and would better fit that kit than Summoner.

The two identities this job was struggling with was divorced for a reason. A re-merging of them will absolutely cause me to drop the class in its entirety in favor of literally any of the other classes that do not suffer from this sort of thematic confusion.