The league is meant to be for S3 racers, so I do not know about vouchers to a demo user could be possible. Maybe if they have an additional account that is demo they could receive a voucher code.
I have been trying to think of prizes myself... however my event will be offline, and in person, on 10 racing cockpits that I am providing.
I hope to do this at as many car shows as I can.
Attached is a rough draft of a potential flyer.
I will be charging an entry fee, to cover the prize though.
My prize being $100 cash, and or, a free rental of my Simulator Trailer.
Will you charge an entry fee?
This will make it easer to give better prizes, as will a sponsor.
If you charge $10 from 20 drivers, you have $200 to play with, give it ALL to the winner, or keep half for charity, or server costs.
How are you going to police cheaters?
Prizes are the number one reason someone may actually try to cheat in LFS. It will be easy to catch a car with 1000% speed boost, but it will be more difficult to catch the crafty cheater with a simple 5% improvement in speed. This is what has stopped me from bothering to organize online races.
Your event being online, could be spread out over a week, by racing for points.
Allowing more people to enter when they have the time.
Too narrowly thought. There is always few people who just gives them to other person away. Sure, it is more like the prize winner can do anything he wants of it.