A 3 warrior rule seems OK.....but only on the limit that it must have 5 to expand past the first shire.

The notion of blocking....is a very tempting one if you can use the first knights just to soak up money from 5 shires for themselves.

But at 3 on 1 it is still not best, because the capital makes a lot of money alone.
I think the word is, Farming.
But warriors can already do that.They just can't be big and do it.

This is a situation that is already seen in some places, where only one knight sits at a castle and sets pay to 100% and tax to 0%. (look back in West Africa in KH)

The second part is...the rule has proven to work already at 5.


Overall though....I think since the game builds so slow, it is worth considering a 3 warrior minimum for the games first 50 years. (With the tool that says need 5 warriors to grow past 1 province. And return to 1 province if go back to less than 5 wariors for over 14 days.)