I wanted to make a data pack to mimic the Anvil Enchantments mod (available at https://www.curseforge.com/minecraft/mc-mods/anvil-enchantments for MC 1.9 through 1.12.2), but apparently Nbt Crafting does not yet (as of nbtcrafting-2.0.0-alpha.30+mc1.15.2) support item counts for the anvil recipes, meaning the recipes end up cheaper than they really should be (in terms of items, not levels). This is primarily desired for the "ingredient" slot, but others might come up with recipes where it makes sense to have counts in the "base" or "result" slots.

This is a general point of discussion whether ingredients should be able to take more than one item at a time.
It might actually make sense for anvil recipes but not really for any other recipe type.

#56 at least fixed anvil recipes consuming the whole ingredient stack so anvil recipes are generally a little more reliable now.