[Aezeal]

I think ti would be very easy. If you read the modding PDF it should be clear

create a new nation (see manual)
clear the nation (see manual)

and then I think you'd alread have a nation without recruitables

then you could add some starting troops or just do it with a pretender.

I think it's a waste of your time trying to play it though, you won't get far without recruitable mages, certainly not if you don't have blessed troops

Here, try this

I used one of my mods and removed everything that made it a nation. I'm not gonna even try it myself if it doesn't work you'll have to adjust it yourself