This is a very interesting tree. It fixes nitrogen, can be used to retain soil in gullies and grows in tough areas. It is also considered invasive in parts of North America as it forms large stands of only this species which exclude all other species.
Around the world it is used to make charcoal, particle board and stakes to name only a few uses. The seeds and pods are used as cattle and sheep feed but some species contain phenols and tannins which limit their use by humans.
Acacia farnesiana is more of a shrub than a tree and has edible seeds. This article
details some acacia with edible seeds and where they are grown around the world.
So, there are acacia with edible seeds, and you could probably graft them onto your acacia but it's a lot of work and would qualify as original research in horticulture.
Given the challenges of grafting with a species that does not have a long history of grafting I'd rather plant a tree that I like the fruit or seeds of directly.
Edit: Just for clarity you can only graft within a genus. So you cannot graft apple stock on acacia.
This web site seems to be a detailed web site for acacias. You can search for all members of the genus by continent. Theoretically, every acacia listed on the web site is a suitable candidate for grafting. Grafting is not currently practised commercially so no one can tell you how successful you might be. Let us know!