It would be great to support additional movement buffs other than druid and shaman forms.

The level 60 Warlock talent Burning Rush provides a 50% movement speed buff until the player's health runs out. (talent id: 19291, spell id: 111400)
Another example would be the Paladin's level 15 talent Speed of Light which provides a 70% speed bonus for 8 seconds. (talent id: 17565, spell id: 85499)

I thought about trying to support Burning Rush since warlock is my main class these days, but decided against it at some point... though now that I'm thinking about it, I don't remember exactly why, and none of the explanations I can come up with make any sense. I'll think about it some more.

Alright, I still haven't figured out why I didn't want to include Burning Rush, so I've added experimental support for both it and Speed of Light, though I don't have a paladin so I can't guarantee it works, even though I'm pretty sure it should. Since Speed of Light is a cooldown, it requires using the travel form override modifier (default CTRL/STRG, can change at the top of the file).

Any other such abilities you think I should add?

I don't know how I should handle Dash/Stampeding Roar for druids or Spirit Walk for shamans, or even if I should handle them at all. For example, if a shaman presses the button while running, right now it'll activate Ghost Wolf. If he presses it again, should it activate Spirit Walk or cancel Ghost Wolf? When should Spirit Walk be activated without Ghost Wolf? The druid abilities/forms are even more complicated.

Yeah, I was always annoyed by Squire2's configuration too, and when WoD hit it wasn't obvious that Squire3 existed (there was no link from the old page) so I started writing my own. I did try Squire3 but it had the same bugs with shaman Ghost Wolf that each of its predecessors had, and I just didn't feel like waiting for the fixes, arguing with the author again about how macro conditionals work with shapeshifts, and then still dealing with a confusing configuration.

Roll was definitely on the to-do list at some point. PW:S probably won't be included since it requires a target, or if I did include it, it would only work out of combat and always target the player. Sprint will probably require a modifier. Undecided on Unholy Presence (and Aspect of the Cheetah/Pack).

I wouldn't add Stampeding Roar or Spirit Walk either since those are too situational. You don't blow a 2-3min cooldown just "to quickly get away". Situational abilities should not be added, I think.
My gut feeling is this addon is for things that make me move faster that I can toggle on/off. Extending this to ... and things with very short cooldowns lets me add for example Speed of Light.

I've listed some movenent-related spells below, but aren't quite sure which of those should be used by the addon. This list is in no way complete but already shows the amount of spells out there...

Situational (for the record)

• Shaman: Spiritwalker's Grace
• Mage: Icy Floes, Blink
• Druid: Displacer Beast (a blink), Wild Charge
• Hunter: Aspect of the Fox, Disengage
• Goblin racial Rocket Jump

Movement

• Rogue maybe Sprint
• Mage: Blazing Speed
• Druid: Travel Form, Cat Form when inside
• Shaman: Ghost Wolf
• Warlock: Burning Rush
• Paladin: Speed of Light
• Death Knight: Unholy Presence which must toggle back to the previously selected stance, Death's Advance (talent, when triggered)
• Monk: Roll (also works with Chi Torpedo)
• Priest: Power Word: Shield with Body and Soul

P.S. I was using Squire before but prefer the "set and forget" approach of MountMe. Configuring Squire was extremely confusing and I never got it to work the way I wanted.

Added Blazing Speed and Roll/Chi Torpedo in this commit. Not tested yet.

Actually just realized I made them all require the travel form modifier, since I just reused the paladin code and made it general... will have to fix that later.

Added Death's Advance, Aspect of the Cheetah, and Sprint as well. I removed the modifier requirement for all these abilities; they will be used while in combat, or while moving (without a "cast while moving" buff).

At this time I don't plan to add any other abilities, beyond what's already supported (Travel/Cat Form and Ghost Wolf from your list). PW:S isn't specifically a movevement ability. Unholy Presence conflicts with Death's Advance and requires remembering a previous state. Rocket Jump conflicts with class abilities. Dash (not on your list) is too complicated to work into the druid tangle.