The problem is, the Finns were less economically advanced and much, much less populous than the East Slavs. There's no way they can fit the same niche without some serious changes way back in the past.
That said, the 'empire' pictured in the OP is pretty much what you would expect to fall under the influence of a Finnish state, where one to butterfly away Novgorod, keep the Slavs further south by whatever method...