i love getting the charge and then using burning alignment to knock off some guys and then kill off some more with the D6+1 and then finishing off whatever with the steggy. but yes you can!!
though remember if the priest dies, you cant use the abilities of the engine anymore, so be careful of where you charge it as long as you keep it away from units with characters or nasty unit champions, you should be ok.
I know he is a weak little guy with 2 wounds but he still gets the 2+ armour save and the Steg gets to fight in challenges aswell so he's not exactly a knockabout...
If you take the Amulet of Itzl (2+ ward save vs first wound taken). You effectively raise his wounds to 3. That plus the 2+ on the Stegadon will help him last through alot.