We have two proposals out there already:
Brian - Modern F1, more or less Formula libre
Alastair - Rally with Special Stages, Time Bonuses, Night Stages. He suggests using the SCX Escort MkIIs but maybe we could meld this one with one of the above Rally car types?
This one's from me
SCX Le Mans Series GT1/2/3 - that would cover lots of cheap & pretty cars similar to those that raced in our pleasant 2016 UHdDD - Corvette C6R, Ferrari 550 & 360, Aston DBR9, Porsche 911. All with inline RX42 or 42B & adjustable magnets. There's always a pile available at Scale Slot Cars for £20-30.