Im just putting this out there. I was curious if mounts would be considered even romately viable in this game? The maps are extremely linear from what I can tell. But I was curious in what you guys thought? I can see them if this was a massive open world. But maybe they can work here? What are you guys thinking? 
This late in Development mounts are definitely a no go unless someone somehow works it in with modding.
Might work if you got rid of the movement speed cap, balanced movement speed already in the game and then add some sort of item that changes your characters appearance though that would require animation and who knows what else lol. Systematically it might not even be feasible.
But what will the mounts ride when they get tired?
after playing Grim Dawn for years without such a thing personally it would feel pretty odd having any form of mount, ontop of this the player characters move pretty fast as it is in my opinion after a certain point. 
I do remember an old thread where someone suggested the ability to jump and since we have that now who knows maybe we can all have a Zantai or Grava Cat mount to pounce upon our foes.
Grava Cat would work well with items like Cauldron of Excitement and Soiled Trousers
FG Expansion gives us the ability to jump, dash, backflip, teleport. that alone is enough improvement for travel speed.
if GD’s nearly as big as skyrim, then mounts are almost mandatory. otherwise, maybe in GD2 mounts will appear. Sacred 1 and 2 is pretty similar to GD, and they have mounts that blends well into gameplay. so I’m quite sure crate will consider mounts in GD2.
Could that be done for all players? A customizable pet? Maybe it could sell the trash gear for you in town while you continue on with your quest?
maybe try looking at modding section… someone might have made a pet shopper mod that is similar to torchlight…