What if the conditions change drastically?

• Strong omni-present magnetic fields
• Fast rotation
• Global cells (so that surface curvatures matters)
• Very efficient radiation (A-type dwarfs to early M-type supergiants)
• Inefficent radiation (metal-poor stars, M-type dwarfs, brown dwarfs)
• Complex chemistry (molecules, dust)
• Stellar wind
• Strong pulsations

We need a few calibration points very different from solar conditions.