Igni Ferroque is a multiplayer balance mod that sticks closely to the vanilla style while completely reworking key mechanics and adding new units and maps. The aim is to create a whole new balance which should allow much more satisfying gameplay by rewarding good strategy. The name is a latin phrase referring to the scorched earth tactic, meaning "With fire and iron".
Get any updates from the TWC forum post under the downloads section.
Official TWC mod post:
Twcenter.net
I know you said its a multiplayer mod but will this work in the campaign?
I guess you could copy the vanilla campaign folders across and play it?