Hello YogiYang,
It sounds like a very useful tool. Unfortunately, integrating new data sources to a mature low code platform is not easy. For one, there are many features that PostgreSQL has that we rely on; we cannot even easily integrate popular systems like MySQL/MSSQL because they lack important features, even though that would definitely help many organizations.
On the other hand PocketBase appears to have a REST-like interface, which you might be able to call from REI3 to retrieve data regularly.