all it really needs is a modification to the payment system, which of course could take some time lol, then again if that happens i can imagine coupons will drop in ap value to around 50-100ap per to balance it, 1 event participation prize of 500ap is high compared to the say 200 we get for advertising a new game or beta testing browser games ect.
All depends on how generous of a reward people really want, it makes sense for a 500ap one to be redeemed in payment form,
but participation prizes maybe a simple 100ap which allows players to choose a basic reward from the IM. Which of course wouldn't need a payment to redeem.