I had an idea some time ago of a mobile dancer support that focused on quick movement to poke in a hit-and-run manner. Went like this:
Agile feet [Passive]: Auto attacks and spells on enemies grant champion a short burst of speed (half the amount for auto attacks) and the ability to ignore unit collision for a short time.
Dance with me [Q]: Gracefully leaps to target ally, shielding herself + target ally if it's a champion, and granting that ally the effect of her passive for the duration of the shield. Breaking the shield nullifies the effect.
_Tango [W]: _Jump on target enemy champion, forcing target champion to dance as she arrives. Her next auto-attack or spell on that champion will deal bonus magic damage. For a short time, she can either press W again to go back to her initial spot, or press E for Encore.
Encore [E]: After activating Tango, prolongs the dance with enemy champion instead of ending it, increasing the dance duration as well as the bonus damage amplifier.
Waltz [R, channeled spell]: Leaps forward, forcing enemies into a dance where she lands. If at least two enemy champions are hit, begins dancing as well on the spot, creating an AoE that shields allies within its vicinity. The shield refreshes each second as she channels, and quickly fades if Waltz is interrupted.
CC duration and values would need to be tuned appropriately, given that I suck as evaluating numbers, I purposefully let them out, but I liked the idea of a mobile poke buff support.
The issue with that is that it's a kit that can easily make the champion a mage or assassin if the ratios and base values aren't properly tuned. Think of it, and if she has any actual damage to be a legetimate threat, she's fucking impossible to run from. Maybe that's why supports aren't allowed big mobility.