Could AI become the fastest way to validate internal SaaS ideas?

One experiment completely changed how I think about SaaS validation.

Instead of designing an app from scratch, I uploaded an existing Excel application into Claude.

Within minutes I had a working browser prototype.

Not just screens.

Actual functionality.

Connected to a free database.

Running online.

It made me wonder if thousands of internal Excel tools could become niche SaaS products with dramatically less development effort than before.

Obviously you'd still need polish, authentication, deployment, billing, testing, etc.

But for validating an idea?

This workflow is incredibly fast.

Has anyone here built or launched SaaS products starting from existing spreadsheets or internal Excel tools?

I'd be interested in hearing what's worked and what hasn't.