We've got all the major amp flavors covered - Fender, Vox, Marshall, Hiwatt, Mesa, and many, many multiples of their various clones and offshoots, totaling over 250 amps. Add to that 2000+ IRs and countless other 3rd party IRs. Just in the box alone as it comes from the factory that equals over half a million possible combinations. Now add the tweakability of each amp model - change the tubes, the tonestack, the bright cap, the sag, etc. You're at literally million of possibilities, and we're not even looking at most of the other parameters (not to mention effects). I've gotta agree with Cliff. If you can't find the tone in your head with the current offerings, adding more metal (or jazz or blues or country) amps isn't going to magically get you there.
As for simplifying things to attract new buyers, on the surface that might sound useful, but where do you draw the lines? I play in a cover band doing mostly lighter classic rock stuff. I spend most of a gig running through various Fender models. But for some leads, I prefer to use "metal" amps like the HBE or other Marshall variants. Which flavor of the "OS" would I buy?
So some of the TGP participants resist modeling, complaining about spending time tweaking instead of playing. Fine. Let them buy a few multi-thousand dollar amps and a few thousand dollars worth of stompboxes, if that's what they'd prefer. It doesn't affect me. It appears to me that Fractal is selling their modelers about as fast as they can make them. While I'm sure they are always appreciative of new customers, I'm not sure having their business expand to the point where it's no longer a small company would ultimately be beneficial to the guitar playing community. Line 6 is a good example of what happens to product innovation and customer support when a small company becomes a big one. (And that's not a dig at Line 6. They make fine products, but I doubt they'll ever have the customer satisfaction Fractal does.)
And from a software development standpoint, having a variety of "flavors" adds to the complexity of the code or multiple code trees, neither of which is conducive to rapid development and release of new enhancements.