My similar, much less polished project doesn't require you to specify joins ahead of time outside of optionally defining a tree-like table lineage: https://github.com/totalhack/zillion
Zillion uses networkx to create a graph of tables and relationships so it sounds like it's doing something similar.
Views are a nice guardrail but can also get in the way! I've experienced this frustration first hand (and seen it with my business users) when using tools that focus on such a premise. Guess it depends how complex your data model is and how quickly your business is evolving / adding to that model. In the move-fast-break-stuff phase of a company they can get annoying at least.