Ok, the first order of business in the Shimmerverse is to figure out who are going to be Elements of Harmony. Being the Shimmerverse we all know that Sunset Shimmer is going to be the Element of Magic, but for other elements I was thinking something along the lines of:

Trixie- Element of Loyalty
Lightning Dust- Element of Honesty
Nurse Redheart- Element of Kindness

Feel free to make up your own ideas for their elements, but we also need one more earth pony and one more pegasus so that's up for debate as well. I was thinking probably Cheerilee as laughter and Ditzy as Generosity, but like I said it's up for discussion considering this is a collab based universe.

3679432

Well are we going for any sort of theme amongst the elements? Judging by Trixie and Lightning dust they could all be antagonists in the M-verse. So you could do with: -

Iron Will - Element of Kindness - In the form of tough love.
Flim Flam brothers - Joint elements of Generosity - They want to make the world a better place with their inventions, and well make a profit as well if possible.
Cheese Sandwich - Laughter

As you can see I don't necessarily see that there should be a 2/2/2 split of tribes or even that all of them should be ponies.

3679613 I'm kinda going for a sort of Lunaverse feel where everything is different but at the same time kind of the same. One of the biggest parts of that would be keeping the mane 6 ponies (and female).