Expert Script: Movement (Running to be exact!)

Good afternoon, FP!

I was wondering if someone was up to the challenge to code an addon that would switch instant acceleration running to gradually-gaining-speed running.

All that I ask is what is above.

For bonus points: A way to change the acceleration rate and top running speed (Preferably in-game, please!).

If an addon or script exists that fulfills one or both parts of my above description, please give me a link to said addon/script, as that would make my day.

Thank you in advance!

Yours Truly,
Xavier Studios