The problem with this, unless I'm misunderstanding what you're saying, is that the model's responses go into the context. So if it has to reinvent the wheel every session by writing bash scripts (or similar) you're clogging up the context and lowering the quality/focus of the session while also making it more expensive. When you could instead be offloading to a tool whose code never comes into the context, the model only has to handle the tool's output rather than its codebase.

I do agree that better tools, rather than more tools, is the way to go. But any situation where the model has to write its own tools is unlikely to be better.