I agree with some of your points, which is what makes it a tough call I think. But here's the big picture I guess I'm seeing.
Most people are going to enjoy being able to actually compete in a category. Whatever the name of it is, whatever. As long as there is a category that they feel they can actually compete in, and be competitive, that is going to make it more fun for them and actually get them more interested in competing that day, and in the future.
Right now there is a huge gap, which can make people feel disinclined about competing. You want people to enjoy the competition, and to me there's no better way than to actually have people feel that they are able to compete. This can be done by making categories that can accommodate several variations.
1) Stock Appearing - just like it sounds, Stock Appearing. There may be some exceptions here and there, but it's 90% just like the name sounds, stock appearing.
2) True Street 1 - Up to 1 power adder, turbos up to 56mm. This will take care of those that aren't truly meeting the Stock Appearing name. They are guys with tubular mani's, SMIM's, turbos from upgraded yet stock appearing, to bolt on 50trims, evo's with efr4's and all sorts of other stuff that make it not Stock Appearing, S256's, etc. Aimed at people making 300-450hp. People that without this category being in place, would either be waxing up in Stock Appearing making it annoying for people trying to actually be Stock Appearing. Or would end up being in the current True Street category having to compete against a 600hp 6262 powered car and be wondering why they are even trying to compete. I would think this would end up being the largest category as this represents the majority of what people have out on the streets in my opinion.
3) True Street 2 - Similar to what you called True Street before. Aimed at that 500-650hp group with 1 power adder, Turbos up to 62mm. This will get all the GT35/6262/S362 guys out there competing with each other.
4) True Street 3 - This is the guys pushing the term "street", 1 power adder, turbos up to 67mm. Get the guys running T67/6765/S366 competing with each other.
5) Outlaw - Anything goes. John vs. MAP vs. Probezilla vs. DaveH vs. Puerto-power vs. whatever... Anything goes, anything could happen when it comes to cars making that kinda power.
That's all just my opinion, and opinions are like assholes...
Good luck with whatever you guys come up with. I'm sure it'll be fun and a huge event again no matter what!!