Is it possible to trade with Valgsland but ally Agnolia and the win the war against Rumburg?

The title basically.

I want to win with Valken's plan but I need 1 regional power trade partner for that. Since I want to use Agnolia and Wehlen as my Proxies rp wise I can't deal with Lespia. No way in hell is Alvarez getting a monopoly on Sordish Oil, like wtf kind of demand is that anyways. So Valgsland is the only option I have. Any chance to trade with them without having Agnolia abandon me for that dumb island? I need this to work so Intermerkopum can expand into Eastern Merkopa.