I remember thinking at the time "What the hell kind of sense does this make?" with Talia being Control. I mean, why would Control be actively trying to kill itself a half-dozen episodes earlier in "A Spider in the Web." In retrospect, it was just kind of a "Lets get her offstage as quickly as possible" way to wrap up her thread and tie it in to an arc that wasn't really intended for her, thereby killing two birds with one somewhat illogical stone.
I know Takishima was *originally* intended to be Control, but I have no idea who Control would have been once the series started, and there was no Takishima around. I assume Ivonova? That would explain why she seemed to kind of run out of things to do in Season 3...as if her arc had been taken away from her, and so they just had her parking cars until JMS figured out something to do with her. Might also explain why JMS was willing to just let her story arc dangle/disappear with no attempt to wrap it up in Season 5 - maybe he didn't really have anything in mind for her? That's assuming it was intended to be Ivonova, which, for all I know, it wasn't.