Dato
Toga is a big 'NO' Killua dislike, no, he hate! crazy people especially womens. you already saw in anime that from his family, he hate him mother the most (that by the way is another crazy b*tch that is obssessed with him more than his other childrens) another example him willing to order Nanika to kill her if they didn't leave the house.
you make that disgusting b*tch as love interest and I am out. DFQ!! someone even decided it is harem already!?! why would Killua even like a crazy B*tch? like hell he will, it is shown in anime that the only female he hade good relation with is alluka and she is shy/kind type. pretty much he hate his mother because she is crazy, so why would he outright like That crazy b*tch known as Himiko F*cking Toga??