1. A Pokemon could evolve by trading in a certain environment like a city, swamp etc. This is kinda based off the trading/Burmy/Mt coronet evolution idea.
2. Some Pokemon could evolve by interacting with a hidden/specific object in the region. There would be only 1 of these in the whole region. Say if you had a bed Pokemon, it could only evolve by interacting with this one bed in the whole region so it's kinda like Rotom but it evolves.
3. More emphasis on day/light evolutions as the games are called Sun & Moon.
4. More Nincada to Ninjask/Shedinja type evolutions.
5. Evolution lines that make sense and don't feel out of place like Heliolisk, Dedenne and Carbink.
6. More gyroscope type evolutions as the Inkay evolution was cool.
7. A new evolution stone/item
8. There could be a Pokemon that only evolves with a certain egg move. This means you would have breed a Pokemon to get the egg move and level it up. This would increase difficulty but it would also encourage players to get a better nature for their Pokemon before evolving them.
9. For starters, they should give different evolution levels as the standard level 16 and level 36 evolving levels are boring. Maybe, they could evolve via stones or certain environments. This would give more challenge to newer players as they wouldn't just have to evolve their Pokemon.