Heres 5 possible ways the Demis could be obtained.
1. Have a Developer Rate your World 5 Stars
2. Receive at least 1000 Rates
3. Have a Developer visit your map for 15 minutes.
4. Win a forum contest.(Gives a choice. Robo or Demi)
5. Have a Server of 24 people. (Quite easy though :/)
These are just Ideas. I understand you may not agree. Feel free to comment your Ideas.
Problem with theese, Having anything with a dev is a no, it will have the exact same reason why the current method was removed.
Haveing people choose between the two means the demi's will have to be reset and only a few people will get it a year, And seeming they have no powers like robotic it makes it a easy choice to choose robotic,
And not to mention you will have to wait for the updates in order to use them.
The have people in the game or rates are a more reasonable, However we already have unlocks for similar method.