Bring back seasons and make season specific evolutions like eeveelutions, so not forms actual individual evolutions
Evolution variants dependent on both trainer and pokemon genders. Two females, two males, and a mix give different evolutions
An in battle evolution would be sick
Pokemon that were hatched from an egg and not caught
Trade with item variants, different evolutions depending on the item they're holding
Different evolutions with different status effects ie paralyzed evolves into an electric type
Evolve with key items like the gracidea flower
Do we evolve in weather? Goomy does that, right? Well more of those
If custom clothes stay, maybe not evolutions but variants based on what clothes you wear. Like furfrou styles, but those are tied with specific clothes
NPC induced evolution, I don't think we have those; like specific move tutors but they evolve your pokemon
If there were more options to change the music playing, there could be evolutions based on that; like how you can change music at the battle tree, or even the old music player in hgss
Expand area specific evolutions; not just special rocks, but also routes and cities, like on a mountain vs a beachside route
That's all I got atm
