If Tim thinks it may be too complex he knows what he is talking about as he really is the comp man at the moment IMHO. GML is all about transparency and control on a very precise level. A plugin may get you there easier no? I think this guy may get you close to the performance you may desire.
I think that even for "simpler" presets like preamps, very clean units are difficult to sample accurately. The reason is that NAT isn't that accurate below a certain level of harmonic distortion. When deconvolving a clean (unprocessed) test-tone, for instance, I end up with a preset that has 0.002% thd, which is already higher then many modern preamps.