None of this is possible for several reasons.
1) GT hasn't had the NASCAR license for over a decade at this point; that went first to Eutechnyx, then Monster Games, then Motorsport Games. They could make a NASCAR knock-off, but it wouldn't be legal for them to use actual NASCARs.
2) 50 drivers at every single circuit would be insanity. For one, each game would take a major performance hit thanks to having to render potentially several times the amount of cars it was designed for. Even GT7 only has 20 cars per field, so you're asking for 150% more cars per race essentially. Not to mention every single fictional circuit would need redesigning to accommodate the much larger fields (which means all of GT1 btw), and most of the real circuits aside from Le Mans, the Nurburging and maybe one or two others would be unable to run 50 cars.
3) You're asking PD to not only create a massive update for GT7 to add 50 cars to every track, but also go back and update GTS, GT6, GT5, GT4, GT3, GT2, and GT1. That's not happening lmao. Especially since the PS2- and PS1-era GT games would need to be reissued, most likely updated to remove cars and tracks with whom license agreements have expired.
Sorry, but it's just not possible.