Yeah, I agree that Gr.2 would be best-defined by "shell series" like the JGTC/Super GT and DTM. I wonder if South American stock cars could be part of that group, too? Not sure if they have comparable power, though. But it'd be nice if one of the Mercedes cars from DTM could be added, even if it'd potentially be from before the Super GT/DTM merge.
What'd also be interesting, is where Super Silhouette/Group 5/DTMeisterschaft could fit it. Maybe a "Historic Gr.2," since I think DTMasters are a better fit for Gr.2, and the older DTMeisterschaft wouldn't gel as well.
It also seems to me that FIA GT1 is gonna be placed with other Gr.3 cars, as we can see with the McLaren F1 GTR, so I could see the CLK-GTR and R390 GT1 being placed there, too, with LMGTP cars like the TS020 going into Gr.1, especially with Gr.1 being defined by including various sports prototypes.
In that regard, I could see Can-Am cars being added as a "Historic Gr.1" group, maybe even alongside the 1960s prototypes that are already in Gr.X like the Ford Mk.IV and Ferrari 330 P4. I'm quite sure that if BoP also accounted for final gear ratio and downforce, there'd be a lot less flak for placing various cars together, and even less if N-series cars would be ineligible to compete in an N-class when the car in question is not part of the class without changing its power, like how we can see with the X-Bow R and S-FR Racing Concept. Here's how I'd tackle BoP & tuning permissions, in a summary of sorts:
BoP on, tuning disabled = N-series cars can only enter if they come stock as part of that class. In addition to power/weight, the final gear ratio and both downforce values are also changed.
BoP on, tuning enabled = N-series cars can enter even if they don't come part of that group as stock. BoP will also only affect power/weight, and all other metrics may be eligible for tuning.
However, in some cases, only some areas may be tunable, such as the general transmission as a whole, or maybe just the ride height in particular, or a combination thereof while still leaving some tuning options disabled. I think this could simply be titled "Setting Partially Enabled." There could even be limits placed on each metric, much like how you can set a minimum weight/maximum power, except I think there should be the option to set a range for those stats, too, instead of just one end of a limitation.
In both cases, I think it may be best if BoP results in the affected stats being as similar as possible for each car. And that these post-BoP stats should be readily available to be viewed on the official website, as well as the app, and perhaps in-game without needing the player to enter an event first. This would also include the BoP stats that apply to ovals.
Long story short, the race car classification in GTS is a disaster. They’ve tried to lump so many random cars into the same group and then magically BoP them against one another that it completely destroys any realism and immersion, leaving the impression that the cars are actually nothing more than skins at this point.
If PD is going to keep adding historic racecars, and I hope they do, then they need to introduce the proper categories for those cars, not shoe-horn them into existing categories.
There needs to be categories for TCR/BTCC type cars, GT4, GT3, DTM/SuperGT, and then LMP1-H. If they want to add cars like the TS020, the R390, CLK GTR, 911 GT1, etc etc, then they need to add that category to the game, not magically BoP them against cars that are 20 years newer, or group them with Group C cars that are 20 years older. PCARS did this right, in that they have LMP1, LMP2, LMP3, LMP900, FIA GT1, Group C, GTO, Group 4, Group 5, Group 6, Group A, TC, TC1, all as separate categories, plus half a dozen “vintage” catagories.
Personally I’d love to see some of the IMSA GTO cars from the 80s and early 90s, but in their own category. I’d love to see some of the Group 5 Silhouette cars from the 70s, but in their own category. The 3 existing vintage Le Mans prototypes in GrX should be in their own “Vintage Prototype” category.
As far as mixing TC1 cars (DTM and GT500) with Brazilian stock cars, I’m definitely not in favour of that. You have to remember that TC1 cars are wicked fast, and the GT500 cars in particular produce mega downforce (GT500 has open development of aero outside of some standard components, whereas DTM has much more controlled and restrictive aero regs). GT500 cars are as fast, if not faster, than the LMP2 cars that race in WEC and at Le Mans. If PD wanted to expand the Gr2 group to include more than DTM and GT500, the best option would be the DPi cars from IMSA, along with the FIA LMP2 cars. In real life, these cars produce relatively similar lap times, and it wouldn’t be a massive stretch to BoP them against one another. Knowing PD though, they’d probably stick the DPi cars in Gr1 just because they have a similar shape to LMP1 cars, never mind the fact that they’re a whole category lower.
I could see Brazilian stock cars being a much closer match to both Aussie V8 Supercars, and/or NASCAR (or some variation of a North American stock car). Trans-Am cars might be a decent fit for that kind of category as well.
That's a fair point. 
