Ysera is perpetually asleep at the Hall of Storms, and cannot mount.
Instead, she can activate
Dreamwalk (Z) to project a mistral manifestation of Ysera's Visage Form to a target area for 12 seconds with a moderate cooldown, 40 seconds or so. The manifestation cannot be damaged or targeted, deals 82(ish) damage with its attacks, and moves 20% faster than a normal Hero.
The manifestation is controlled directly, and while it is active, Ysera cannot access the global utility of her basic abilities. Instead, they behave as described, as she is
Dreamwalking.
The manifestation collects Experience Globes as if it were a Hero. In addition, it cannot move a certain distance further than the point it its summoned to. This, however, still gives it a rather large area of influence, with roughly the same area as Azmodan's Globe of Annihilation's range.
Maybe let her toggle dreamstate, giving her a new set of abilities - like a cross between Aba hat and DW fly
So moving the mechanic of R2 to her trait/mount button
https://www.heroesfire.com/hots/concept/tyrande-12462