The elemental is a no. There are elementals, but they are a sort of different creature.
The troll would be difficult, as trolls in general are none too bright. I suppose it would be doable, but I would advice against him being an aldonadian. Also, trolls live only about 125-200 years in my stories, I believe. I am also going to say they love technology if they can figure out how to work something.
The human character would have to be reworked loads as there are no rune-magi, at least not in the traditional sense. There were seal magi that worked by binding their spells into rechargeable glyphs that only they could release, but that art is nearly dead, preserved only by way of the scribes, and even they cannot produce the powerful glyphs of old. Also, the height issue would make him a half-giant since humans do not grow more than 8 feet at the very most without some genetic disorder, and those might as well be half-giants for clumsiness. He's doable, but would need much reworking.
I think your best bet would be a completely new character, but I won't force it. If you want to use one of the others, you can, but they need my approval.