This seems like the only solution. Do not copy all of Python’s warts, but offer a curated experience. Microsoft Experience (TM) with fixed APIs, no package management or dealing with ecosystem churn.

It will never work because Python is the ecosystem. Having Python without the ability to tap the huge catalogue of existing software makes the integration worthless. The first thing someone will want to do is use Pandas on a live spreadsheet.

If you read TFA, you'd see that the python env comes with a bunch of the favorites (pandas, matplotlib) baked in.

The use case is someone in Excel who does not want to write VBA. You do not need to offer the entire ecosystem, just a slightly better language to handle more sophisticated modeling needs.