I mean that's what the PPWR directive is already? It's a single set of laws that applies to all member states. They just didn't write any interop so every country has its own system and registration.

If it was just single registration for EU and paying for each kg of plastic or electronics to member states (like you do with VAT already via VAT-OSS) then it wouldn't be such a big deal.

Even if you didn't have any agreement with recycling companies in each member state and you had to pay the highest per-kg fees it would still be manageable for small sellers.

Meanwhile if you want to sell a single circuit board you're looking at several thousand euro in registration fees and several months for processing just to sell legally to 4-5 countries in EU.