So many tracks are just sitting there in a menu, if Phil was smart he would would have relaunched a deluxe edition with Master Chief and captain Price karts.
They have quite a lot of porting potential in their back catalogue but whether they do or not is another thing. Fable Anniversary is on Steam but not II or III, I think Viva Piñata and Nuts & Bolts would do really well as £20 digital releases on Steam and Switch.
ShadPS4 (soon).
I suspect they had such bare-bones multiplayer, everything (dlc etc) was stored on your local machine without an item server keeping track of it.
It would have been a regedit away from full unlocks on PC.