This may be a longshot suggestion, but I noticed I have a dlc-pack lying around still untouched because I never saw someone organize races with it. I have no idea if it's actually great or not and the pricing is a bit silly, but I'm talking about KartSim. Maybe this could be something in the future, if only a small series with the 3 tracks from the original pack. I loved the original ISI Karts as strange as they seemed to be, so I think this could be worth a try
I suspect it's very unlikely we would get enough entries due to the high price of the DLC and the limited or non-existence of interest expressed at SRO in the past.
