[quote=Leidenschaft]
The Companions, as far as I can remember, aren't supposed to get involved in wars and whatnot unless shit hits the fan with the force of a panzerfaust. But Balgruuf would be a pretty cool High King.
[/quote]

That really depends on who is currently the leader/Harbinger, the reason they did not take part in the civil war was largely due to political reasons. No where is it ever said they can't get involved in a war, that would be missing out on an entire market for them anyhow.