Bowser's Galaxy Reactor
This race will be made into sections. All transitions will be made with a Glider Jump. Anti-Gravity would be perfect on this kind of stage, and with Mario Party 8 and 9 giving Bowser a space themed level, I'm surprised they haven't done something like this before.
Racers start at the Comet Observatory, making a couple turns before blasting out via Launch Star. This would have a cannon like effect. Players would land on a "broken castle" like effect. Perhaps the Spotlights could be like the boost pads in Cloutdtop Cruise, where you can only go through them when they're not going to damage you. After this you would go off a Glider jump, moving into the lava section. This would be like something you'd expect in a Bowser Castle stage with lava, fire bars, etc. Enter Section 2.
Section 2 moves on to the Ice Planet. With Ice blocks and maybe put Freezies there as obstacles. If a player accidentally falls off, there would be drive-able water that people could use for an easier but slower route. Then you'd head over to the quicksand planet, filled with pokeys and occasional quicksand pits. After all this players head into the Space Junk area. There would exist the fancy platforms, and this is a fairly simple area except for a couple fire bars. Moving on to Section 3.
Section 3 leads into the tower planet. Racers are driving head-on and must avoid bullet bills that are being shot at them like Airship Fortress. Then the players race on The Pathway that would normally lead to Bowser's battle. But instead of the battle, at the end of the pathway players drive into a track off a longer Glider section that's in the Black Hole. They must be careful to avoid the asteroids and debris that is floating around. There is Boost rings and a ground just in case. Like the asteroid section in MK7's Rainbow Road Section 3. A couple more turns and boost pads after this, and players jump out of the black hole onto Peach's Castle grounds, the Finish line right there.