I think your starting point is to start Googling and ask around and find out costs -
How much is -
Venue Hire? Lighting hire? Mannequin hire? Wall dividers? Any insurance costs? Hire if required for people to do professional lighting and set up? Can any of these be done as a favour/low cost by County fans and/or in exchange for publicity.
Then go "I need X amount of money and X amount of volunteers to make this a goer, can I make enough through crowdfunding/entrance fee to at least cover costs".
Get the costs and put it out there.
Although I'm not sure about holding it a time and/or Venue away from EP on/including a match day, that might be over-estimating the audience possibly? Would enough people be interested enough to make a special trip outside of a match day and to a venue that isn't EP.
I'm not poo-pooing the idea, I'd love to see it come off, but these are some of the things to think about/look at it.
My suggestion is, do some groundwork, and see if it's a goer.
If you come back with some of that done and a more detailed plan, then the Co-op Board can look at it, and hopefully put our backing in terms of suppprt/volunteers/publicity behind it.
That's the way the Half-marathon got off the ground, and the Co-op Football Season calendars.