Questmania, the game that was supposed to follow Trackmania and Shootmania, and made literally no sense whatsoever from the moment it was announced.
They have a Twitter account they've never used
I just want to know what the hell this was going to look like
This is also an excellent candidate. It was announced 8 years ago. Nadeo still claims it's on like Donkey Kong, but they are concentrating on getting ShootMania in an ideal spot first... which is odd, considering the game's playerbase is pretty much dead. Also instead of uniting TrackMania like announced back then they decided to split it all into different smaller projects, plus that compilation of sorts that is Turbo which got basically 0 post-launch support unlike other titles. They wanted to create a giant hub where you can create tracks, shooter maps and RPGs under the same engine, the same roof, but inside different games that, however, function similarly at their core. They had this great concept of Maniaplanets and zones and such to have local and global communities, leaderboards, but it seems like it all went moot when they decided to stop with the union of games and release smaller, less connected titles instead.
So, how does QuestMania fit into all this? Nadeo claims it's still happening so we have to take their word for it I guess. We're almost in 2019 now, TrackMania's relevance is nowhere near where it was a decade ago (unfortunately), ShootMania failed to make an impact, there are other games out there to create RPGs and at this point I don't know if people care, nor if such an ambitious project has enough of a playerbase still interested. Such a project only makes sense if there's a large community of people playing and creating, because making a somewhat competent mini-RPG still requires more effort than making a simple track (and this is coming from someone who would spend dozens of hours on a single track in the original TrackMania games). I'd really want to see it done, even as an Early Access title, just to see what they are trying to do here exactly almost a decade after it was announced. I don't think Nadeo played their cards well regarding the whole Mania project after canning the excellent base of TrackMania United Forever to instead release smaller one environment games with half the features, but QuestMania remains an interesting concept that I'd love to play.