Here's a quick example that I just thought of:

Dodore Doublet: looks the same as it does now.

Dodore Doublet +1: Tiny Dodore wings sprout from the back

Dodore Doublet +2: Medium Dodore wings sprout from the back

Dodore Doublet +3: Large Dodore wings sprout from the back, and the character has a subtle, purplish haze around their body (like the purple fog Dodore spawn condition in Mor Dhona).