MPC vs Grand Campaign

I've only really played MP on NTW. Are their many main faction units available in the Grand Campaign for instance that aren't available for multi player battles? I heard you could have Irish Legion for France. It seems a shame that we can't have them an any others as choices for multi-player.

I've never even heard of this "Irish legion" you may have been duped! Oh, and you can't have some units, IE penisular campaign extras in grand MPC

ah maybe they were using a mod