t1 has got it ...

simple version:

create a faction named "x"

faction "x" is only available online and can only be played against itself.. x vs x

this faction would roughly resemble the setup from shogun same units/stats adjusted for the new game engine

one step further....

make this faction have its own unit stat text file... that way if the mp community decides it wants to tweak it with a stat patch it wont throw regular games out of sync vs non "x" faction players.

plz ca... this is a simple idea.. very easy to add.. call it competitive mode or something... heck... you could even put that on the box somewhere ...

1000's of troops...
castle sieges...
online play in regular and competitive modes...

:)