In the end, I couldn't overcome my sleepiness.
So this morning I downloaded the expansion and updated the main game, and just now played through to unlocking the S1 class.
My current impression is that this is a very well done DLC.
The class based progression system is fine except that this affects free roam.
All DLC cars are locked. But by completing challenges they are added to autoshow. they finally got the "right" unlock system back since FM2.
I was negative about the floating map in the sky, but when I actually play it, this landscape is not bad. Each biome has a lot of character and I never get tired of seeing it.
And the HW style roads...I hated the plastic roads in FH3, they were so slippery even in AWD, and in RWD...needless to say.
But this time the plastic roads have enough grip. Of course it seems slightly lower than tarmac, but no complaints.
I didn't like FH5 much. Lots of bugs, live service that is all about "user engagement" numbers rather than user delight. It was more frustrating than enjoyable. But I find this DLC to be one of the most enjoyable expansions in this game, or any recent Horizon series.
Playground Games, you guys did a great job!
Note: It seems they have added a new bug to the game in an update.
If your machine collection notification is at 9+ you might want to take a look at your collection menu.
All the manufacturer complete bonuses are available again.