It's not even that complex, just keep a hash of position fixes and MAC addresses and overwrite it occasionally. I could probably hack something "good enough" on my pinephone in under an hour.
There's the global network where everyone is sharing fixes though... oof I don't really even want to be part of that.
It's not complex to code a proof of concept good enough to check assumptions with a possible implementation. Now, for the implementation and roll out as a product you would be probably months to years away.
Why we developers like to be so optimistic about our own creations? I can definitely hack a lot of PoCs in short time if I don't have to care about security, other users and so on, the moment you start to introduce the real world into your little PoC is usually when a hack that took 1 day explodes into a months-long project. And for good reasons.
Last time I looked into this, Apple actually used quite a bit of clever crypto engineering to protect user privacy. It's not just a big database of locations that Apple keeps.
There's the global network where everyone is sharing fixes though... oof I don't really even want to be part of that.