What you described sound even more complicated than the current format. Varying period-accurate tyres (for every single classic car) of both road and slick variety, plus modern road, sport, semi slick and slick tyres, and a highly controlled set of tyre compounds for race cars. Not only is this gonna need a lot of manpower to get period-accurate grip levels for classic cars, tyres that may not even exist anymore, it's also a lot more limiting than what we have now.
If you want to have a classic muscle car sliding about like it would on classic rubber, find that balance for yourself with the compounds available, you have a very straightforward classification of them already. But someone else might just want to use slicks on it, or something in between.
We already have varying degrees of grip, plus varying tyre wear for the option of strategy for those that take the racing more seriously (which is also adjustable), your idea seems to want it to be locked for each car to a specific experience. GT is not about being absolutely strict, nor should it be.