Problem: 

SQL is quite powerful, but writing large queries is cumbersome and error prone. Another problem is, that SQL has specific dialects or the different databases (T-SQL for MS SQL Server, PL-SQL for Oracle DB, etc.)

Solution:

Why not take a standard ORM technology (like .Net Entity Framework) and implementing it as a standard as an alternative to Advanced SQL for quering of database Entities inside of Service Studio. Entity Framework is quite powerful, a standard in the C# and .Net world, quite flexible, stable and optimized and allows for querieng of databases from different providers (MS SQL, Oracle, PostgreSQL, etc.) with just a simple configuration.

As alternative, a standard .Net Entity Framework (Core) could be integrated for usage with the existing database via an official Extension, supported by Outsystems.