I have had this idea for a long time now, and I don't know if anyone already sent anything regarding this but:
I had the idea to create saddles for mounts that will allow us to socket some jewels on it. (end-game content lvl 140+)
The lower tiers of saddles would be lootable on bosses in endgame and from there we could upgrade it to a high tier via crafting and maybe special reagents.
Depending on which tier you got you can socket from 1 to 4 different jewels (shapes depending on the ones you choose to craft kind of like decks)
And with that adding some mount speed jewels ranging from 1% up to 5% and maybe 10% in the future.
Also maybe have a damage jewel limit up to 5% (depending also on the base damage the mount has)
Exemple: I have a gulthure on and it has 3% damage, I would only be able to socket a 2% damage of this school damage.
Every jewels should have a limit of % we can have of it, and maybe with this releasing some resist (% not +) jewels only for mount saddles?
The saddles (depending on tiers & school) should also have a special effect like pet jewels, an aura, a trail, a whisp, or something subtle to make more character customization.
------------------------------------------
This is a side idea but since you are focusing on wizards playing dual schools, I was thinking of:
Making Dual schools jewels & Astral schools jewels. (Exemple: 5% & 5% Damage, or 5% , 5% 5% Pierce Jewels)
And one last thing, maybe have some new shadow and astral spells jewels to make the hitting spells more usable, like some dual school damage jewels: 5% + 5% Damage Jewel, or some Shadow Rating jewels (Mounts only, or replacing power pip rating).
------------------------------------------
Thank you for reading, Please take this idea into consideration.
& 5% 
Damage, or 5% 
, 5% 
5% 
Pierce Jewels)
Damage Jewel, or some Shadow Rating jewels (Mounts only, or replacing power pip rating).