Well, AC never had as many options or bells/whistles as PCars, but I'm pretty confident they will fit everything into the console build that they can (and they've said many times it should basically be exactly like the PC version). I hope they didn't have to cut too much stuff to make concessions for the console hardware, but it's possible.
The flames used to be a basic .png that just flashed on and off. A few updates ago they made the flames animated and they look quite slick, but I'm not sure how resource hungry they are (probably more than we'd think).
It's been discussed over and over on the AC forums with Stefano, unfortunately things we think are easy aren't always that easy (there's a lot more to it than just picking a set of cars and tracks). Remember, this engine was originally designed to only have a handful of cars and tracks and that's about it, so making it do things it wasn't designed for isn't always that easy. But, Stefano has said he's working on it and a custom championship builder is likely on its way sooner than later, so just have a bit of patience. 👍