Let's fix walnut trees! Because as it is,, you have to rip all the leaves off in the hopes of getting a single nut. So instead, let's do this:
Like fruit trees, nut trees flower each year, spawn nuts, and can be harvested. Individual seeds are reflavored as a handful, to make up for their smaller size and to take into consideration that not every seed is going to be fertile. Unlike fruit trees, you plant them from seed. For balance, and to bring them in line with rl trees, new nut trees take multiple years of growth for their first crop.
While we're at it, let's make acorns edible! Like in real life, you have to leach the tannins out before they're edible. Unlike in real life, let's make this something you can do in a barrel. Maybe make them a source for weak and strong tannin for tanning, while we're at it. Grind the acorns, age them in a barrel for a couple of days, and receive acorn flour (or maybe go straight to dough?) and weak tannin.
Once we have this framework, it'd be simple to add more tree nut. Hazelnuts, almonds, cashews (with bonus cashew fruit!), etc.