Antares Mic Modeler gets bashed a lot because it doesn't really achieve its goal, but I've found that if you get past the notion of "this will sound like an MD421 exactly" that it can be an interesting EQ tool on some types of material. It's been years since I last used it but if you don't take it too seriously and just play around with it, you can get some cool results as I remember.
Impulses are probably a good way to approach this, assuming you create an impulse of a mic in a dead room. But it's not going to sound like the original source miked through the impulsed mic, it's going to sound like the mic you actually used being pumped through an impulse of a different mic. Again, this could totally sound cool in its own way.
I think the important thing with all emulation technology is to not think of it as "the same" but to think of it as "close enough, but different." The same exact settings in a digital emulator won't sound like those settings on the analog device, no matter how good them modeling is.
I don't think that there's going to be a replacement for owning a great mic collection, but if you have a few good dynamic mics and a couple of decent condensers you can probably achieve just about anything you want if you develop your skills. Many of the best sounding records ever made were done with relatively inexpensive mics.