My understanding is that these modern load boxes are using DSP modeling of Impulse Responses to get the "sound". It might be cheaper/easier to get a set of impulse responses and use them.
I contacted this guy. I have everything to do this. Mesa amp, GP-1000, Stratocaster, Suhr(on the way).
If it does not sound like this. I'm pouring gasoline on a pile of shit and burning it all.
As for "thin" guitar sounds I recommend smaller speakers(they tend to sound woolier than their bigger brethren, say using 10 or even 8" instead of a 12+), smaller amps(15-20 watt with and 8-10" speaker combo), and/or ribbon microphone(IME just about any ribbon will sound darker/thicker than most dynamics and pretty much any condenser).
Then a bit of very short delay and/or phase/flange and presto thick a_ _ guitars>YMMV