That is not a technology problem. Every tried to get a law passed?

What about a unified interface which takes into account each sub-jurisdiction's arcane rules and gives you advice how to handle things?

Of course you would be paying to keep the product up to date with local laws.

That sounds like a good idea, but don't underestimate just how complex law and tax is in each country. You need hundreds of lawyers to sift through this. There are so many law and accounting consultants for a reason.

I once met an SAP-contractor who was paid 5 digit amounts for implementing 1000 loc modules that was required because a tiny paragraph of some pension-law in a single country was updated.