Hey Melgrimm,
that sounds like a solid way to add custom emotes! Any animation is generally supported inside a skill.
The normal flow also uses a "prepareAnimation" which plays when you first select the skill, before confirming a target, but you can skip that and make the skill cast instantly by setting "noprepare" in the PrepareAnimationInit and PrepareAnimationLoop properties.
The Shout skill SpiritVision in Shared > SkillData > Shout is a good example to look at
Sincerely,
Kevin