Grafting improved varieties to established native forest

I have a large portion of my land in native forest. I noticed several persimmons and large cherry trees, however they do not produce very well, if any (only been at current location less than six months).

I have the idea of converting the existing trees to more useful trees via grafting. I could graft improved varieties of persimmons to my already bearing age persimmon trees.

I'd like to graft overcup oak (type of bur oak with plum sized acorns) to my existing white oaks.

Could I graft chokecherry to my large native cherry trees?

Just read you could graft between plants of the same genus, but new to this so not sure if its true?

Any other grafting ideas of large cherry and persimmon trees?

In zone 8