Yuui is all for trying to communicate with it rather than trying to fight. Knowing him he'll probably keep trying even if it chooses to attack them instead. Reason will always win out in the end, right?

He has a couple of overprotective pokémon with him who might be a bit less amendable to the peace talk idea if the Heatran ends up attacking them though.

(Also I'm interested in what the mods will do with the reincarnation thing. Sound like it could put a pretty interesting twist on things.)