An open aggregator would be like an aggregator, but good.

Aggregators allow zero-friction movement of data within their pocket universe.

This unlocks a lot of innovation and value (as long as the aggregator allows 3Ps flexibility to do interesting things).

Although the aggregator themselves can, of course, peek whenever they want--you must deeply, fundamentally trust them as a user.

Open systems are composed of many different entities.

You can't share data across different entities willy nilly.

But if you could change the laws of physics to allow data to move across subcomponents in an open system safely, then it's possible to get the benefits of an aggregator (low-friction and standardization) with the benefits of open (no one entity in control, no entity that can see all your data, permissionless innovation, ubiquitous self-accelerating ecosystem)