I don't think poses are any issue for them when making a mount.
-Cloud Mallow, you cling to the back of.
-Namazu Mikoshi you hang off the side.
-Deathclaw holds you dangling like a ragdoll.
-Fat Choco has you holding sticks dangling food.
Not to mention the fact that they've already modeled it for Hyur. Granted it takes more work to scale for other races, but honestly I think it's not unreasonable to hope for it to be attainable somewhere down the line.
The only problem is, it may only show up in the cash shop for some unreasonable amount of money instead of as an actual raid reward.