The worse part about fantasy tracks in Forza is that they tend to gut the larger versions of the track in future titles.
Rally di Positano went from an awesome long technical track to a short forgettable one.
New York went from a long track with long straights and sharp corners to a track that was just boring.
Fujimi Kaido is a great track.
Bernese Alps was a nice distraction from more realistic tracks but not the best.
Maple Valley is probably the best all-round fictional track they have made.
I would like to see Willow Springs Raceway make it into FM8.
Any returning fantasy track definitely needs proper pit lanes.
New York's downgrade was awful, however the version with all the tire chicanes was pretty hilarious... not good, but hilarious.
I feel the opposite about Maple Valley though, that track is full of noob-trap corners and is generally a pretty terrible racing experience, and even though it looks like it should be fun to just drive, I find it to be understeer city. Granted, for racing it's not the pile up that Prague/Rio/Dubai often are, because Maple Valley actually has run off area... But that's almost worse in some ways. People just fly off the track and disappear and after the first lap its just hotlapping for everyone, where as at least at those crash places groups of people get into a massive crash, then continue racing with each other again as they all get going. I used to like it in the FM1 days, but I dunno what I was thinking then, and I can't remember the last time I had a good race around that place.
At first I thought the Maple Valley remake would be an improvement but I think it's actually worse now. Moving the pitlane so that you have to brake at the apex of a corner that is flat in 90% of cars to get into it is a terrible decision, then the way they designed the exit wall for the final corner means that if you crash while trying to avoid someone going into the pits, the wall angle sends you right back out into the track to collect more cars passing by and make the wreck even bigger.
For me, the FM1 fantasy tracks were by far and away the best they have done, with Alpine Ring being the best and Maple Valley being the worst. I think it would be fun to see them all remastered for the new game. I know some would argue "we don't need Blue Mountains because we have Bathurst" or "we already have Daytona, we don't need Sunset Peninsula Infield" but those tracks had their own character. Blue Mountains would probably actually be better than Bathurst for public lobby tier racing as it's noticeably wider than Bathurst, and Sunset Infield's layout was significantly different (and imo much more fun/interesting) than Daytona's roval layout.
I think Rio de Janeiro should be removed in FM8, or at least, restyled in a way where it's suitable for safe, clean racing and is good for overtaking. Some of the layouts just lead to utter madness, especially in online races.
But... they're going to have to use real roads, like how the city tracks of PGR were made.
Rio has grown on me and I kinda see it as our Macau, but yeah it's not a very good race track in general. Not that it was perfect, but they could just replace it with FM1's Rio street circuit and it would be an improvement for the quality of racing.
Rio's wildness can be fun though with competent drivers that don't just crash every 3 corners, and it's one of the few tracks in the game (along with Bathurst, Long Beach and the Nordschleife) where you can't just run 10/10ths all the time with minimal risk, so it can be interesting.
Rio is only marginally worse for it than the others though, Prague always has a ton of death in the bridge/alley/chicane section, and Dubai's mountain section and tunnel always have a bunch of crashes.