An endurance series is something I'd consider doing at weekends.
They could include all the GT3 cars, the FGT, the Corvette and the HPD as maybe a 3 or 4 class race.
If they include cars that already have a series in their own, it cuts down on the punt of practice required.
What i'd mentioned elsewhere, was that IMO it'd be worth running a season of it in a similar way that the 2.4h RW race was done, im not sure if every round of that is similar or if its just the 2.4h race due to its length, but if they had a race each week but only 4 time-slots, like RW, and at least that way everyone is forced to come together at a specific time, rather than saying theres a race every 2-4h every day, and you have mostly unofficial races and a handful of official ones with 10-20 cars with a tiny amount being in your class.
Push everyone together, and you're far more likely to get multiple splits plus people realise they need to treat it like a real race where they cant repeat it in a few hours.
The problem with endurance races is for every person that would like longer races there's a hundred or more that want the short 'instant gratification' races. The Radical series used to be 45 minute races, not long by any means and I really liked that length, enough time to get settled down into the race so no need to rush the start. But by 'popular demand' they reduced it to 30 minutes, participation went up but it changed the whole approach to the race for me.
And then there's multi-class, the problem here is for every person wanting to run and do well in a slower car/class there's a shed load more that just want to win the race, hence why the HPD is so popular, and why the Z4 was the primary GT3 car last season, people don't want to win their class, they want to win the race.
The first paragraph is exactly what i went through with BL earlier. Dont like long races, dont enter. Simple, surely.
I'd even propose the idea that instead of splitting series up between those who want instant gratification and those who want a realistic experience, maybe offer a couple of specific timeslots within the schedule which are designated for longer length. Even if it was just weekends like i mentioned about RW. Mon-Fri 12x 30min, Sat-Sun 8x30min, 4x 90min.
But as far as im concerned its alright having 9x 30min, 3x 70min races to a season, but anyone who's seen the GT3 series in both formats will have seen the attitudes are completely different. If people had the same attitude in shorter races it'd be fine, but everyone is so eager to charge
People picked the Z4 cos theres only 1 winner. Not picking Riley, FGT or RUF cos its not the outright winner is lame, you're probably right about a lot of peoples reasons, but surely 2/3 of the people signing up know they probably wont be the fastest there.
Ive done a couple of smaller grids, 12-18, and im 2500 and ive been 2-5th rated in there. So a lot of drivers are obviously lower, yet at least half the grid is HPD.