The idea is very simple.
You come to a website and you see a certain coin is taking the lead as the biggest shitcoin right now!
When I think of this I imagine a pile of poop with a wooden sign stuck in it, slightly tilted, on which you can see the name and logo of a certain crypto coin.
The interesting part is that you can pay to have any crypto coin on the said sign.
Lets say I have to pay $1 to change the biggest shitcoin to any other coin of my choice.
For this service you could accept BTC, ETH, XRP, LTC, NANO etc cryptocoins.
Perhaps you could use https://www.coinpayments.net/ payment method. You could create a system where the user chooses which coin to pay for and the user would then choose in which crypto coin to pay with and each transaction has it own ID, so you know which coin the user has paid for.
Once the funds are in, you have to switch update the crypto coin on the sign.
To market this I would go around various crypto communities spreading the news about the biggest shitcoin of all time which can be found on a certain website!
Two cool available domain names as of November 1, 2019