When I initially submitted it would be for the purpose of outrunning zombies easier as well as picking stuff up faster Some of the boss zombies get drastic increases in speed and in some levels pick up are spread fairly far apart. I would think something along the lines of modifying the movement mod stat would be ideal.
However as you progress through levels and gear you can easily start moving faster than the bosses so might not be as useful as I initially thought.
It's how the option request system works. Not to worry, tho, if it's determined that an option isn't possible then all credits will be refunded for the member that requested the option and those that voted to fund it.