For some reason, I think the original dragon would be just called Kyurem, since it seems like he is the main element of the trio.

I really don't like the name "Vahirom" for some reason though…

Hmm… seems a bit off to me. I understand trying to come up with what the fusion of Reshiram, Zekrom and Kyurem "should" be, but parts of it doesn't make sense.

Defensive stats are greater than Offensive stats which is weird since all 3 of the dragons prioritize offense over defense. Steel typing has no relevance aside from Reshiram's resistance and Kyurem's weakness to it. The Ability doesn't seem right for an Original Dragon. Why give it Meteor Mash if it's going to get a stronger/more accurate version of the move in 7 levels. The option to learn HM01 worth it. "Infinite Grey Pokemon".

All in all the Original Dragon there could use some adjustments. Personally, I prefer this version: