I don't see why a level requirement would be needed. A proper gold/MC cost serves the same purpose without throwing arbitrary level requirements into the mix.
I also think that the starter mount would be a nice addition as early as Riversdale, simply because there is a lot of walking in the Farmland content with no direct teleports available to get there.
What do you think about "account-wide" mount system? (like WoW have currently)
Acquired mounts saved to the vault code, so player can start new hero and use his mounts (and show his coolness!).
With such system you can make status item from mounts, giving them for: achievements / low drop chance from powerful bosses / high cost (not sure about last, player can reload after buy to return Gold&MC)
Or you can mix two systems:
- epic rare cool mounts saved to the vault code
- normal Gold&MC / Quest reward mounts saved to the hero code
For example hero will save 3 buyable/quest mounts:
- in Riversdale for Gold (slow speed);
- in Mythargas for Gold&MC (normal speed);
- epic quest for d4 (high speed).
And you have a place for 8 epic mounts, at least 3 can be achieved for example:
- all 6 base classes at level 25;
- all 12 advanced classes at level 50;
- 1000 boss kills;
- and 5 remaining mounts can be dropped from bosses with low chance.
Also I think all epic mounts must have almost similar stats, so difference between them will be pure vanity.
Oh I assumed they'd remove your ability to attack, but increase your movement speed. There'd likely be a mount/dismount button somewhere (this button could probably go in the backpack, this should make Alex happy

)
I dont *think* mounting/dismounting should matter in or out of combat, but I guess if movespeed is increased by a lot this could potentially lead to cheesing certain boss encounters maybe, perhaps limitations could be placed if issues do arise.
Actually, Mount/Dismount button can be placed to the hero command card, Rest button will be removed in next update anyway

This button can be hidden if player doesn't have any mounts, or it can display error "You don't have any mounts, visit stables in nearest city to learn more".
Not sure better use Mount/Dismount button and add NPC stableman, so you can select your current mount from obtained list.
Or
Add spellbook with mounts to the hero, so you can select mount "on the fly", but this will require some dismount rules (like dismount on attack order / any ability use).
"Summon mount only when player is out of combat" rule isn't important for PvE (maybe makes fleeing easier), but important for PvP aspects.
Running on mount to the combat is normal I think, but need some risk, to make "run through all mob packs" idea a gamble, for example:
- Chance to Daze (-50% speed) mount for 3 seconds every time when hero injured. (like WoW daze from back system)
- Chance to damage the mount instead rider, so he could die right in the mob pack.
- Mount speed ups over time (for example start from 250 MS and every second gain +10% speed up to 11 stacks if moving), each hit will remove 1 speed stack, each crit removes 2 stacks. (can be a good base for unique mount system with different base speeds, max stacks and bonus speed per stack. So you can make Mythargas race event

but it's a bit overkill)