Recently we played a huge multiplayer game loosly based on the Battle of Pelennor.

It was an alternative narrative to accomidate the armies we currently had.

Gandalf did not fall in Moria, he spent his time recruiting the aid of the Dwarves and Elves rather than going to Rohan.
Consequently, he never went to Edoras and hence Theodred was left under the Thrall of Sauruman. The Battle of Helms deep never happened so the armies of Sauron were reinforced by the armies of Isenguard on the second turn with Rohan turning up in the 3rd turn for Gondor. The Evil and good forces were to be surprised by a isenguard and rohan changing to sides and forming their own alliance against both side, In turn 4.

The game took all day with the victory condition being simply 'Take the Gates'

Good eventually won but Lost Aragorn, Gandalf, Pippin, Elrohir, Elladan, Fararmir so a moral victory to Evil

http://www.cheltenhamwarchiefs.co.uk/id29.html

The WotR sytem held up very well with such huge armies. It was a real laugh with everyone playing to the spirit.