(I shouldn't post from memory - I'll probably turn out to be wrong, but...)
I seem to remember the Lordz saying they hadn't done a campaign for NTW because the battles wouldn't work properly. I think their battles rely on scripting to get the appropriate Napoleonic style of warfare and you can't to my knowledge script battles that occur during the campaign.

If you can't see any campaign option in their menu I assume they probably modded it out using rome.lnt ? You could experiment with re-instating that option by copying the original rome.lnt file back into the data/menu folder.

You'd need to then probably make appropriate map from scratch - unless you're happy placing N2 factions on vanilla Mediterranean map. You'd also probably need to put recruitment lines for all the new units in export_descr_buildings.txt as I doubt they did that. You probably wouldn't have triggers set up for acquiring appropriate traits / ancillaries etc... Basically it would be a lot of work to achieve something they didn't do because they thought it wouldn't work properly anyway........



Erm, have fun if you try - but bear in mind it would likely need to be for personal use only.