@DanRufola you may want to check out the links to Uber H3 and Google S2 earlier in this thread. Both of these technologies are designed to solve global addressing down to very fine spatial resolutions.
Using either global discretization, you should be able to compute “coverings” of an arbitrary geospatial polygon. Here is an example app that lets you compute S2 coverings for simply polgyons; it’s not too difficult to work with a library exposing interfaces for S2/H3 to extend this to arbitrary polygons (at least simple ones). You can then uniquely compute a set of cells on each grid that define the cover for a polygon, and then hash that… although to be honest what you’re describing is kind of the purpose of S2/H3 in the first place, so hopefully you can just compute the list of cell IDs that cover a polygon directly and save that.