from the perspective of the studio, it would be best to have lots of different amps to have options available for your clients, however, buying all the amps out there is NOT a feasible option so i'd agree with the preview poster about having the guitarist bring in their own amp for their own tone.
I'm kinda fortunate that I can brew my own amps. The tack I'm taking right now is to make small Single-Ended 8 watt amps, all of different voicing. I got bit by the DIY bug again. I had a Transformer set wound for it and bought several tube sockets again.
First on my agenda is a VOX-voiced amp. I won't do Fender and Marshall anymore, I have full-sized versions of those already. Oh I don't know what's next after that (and the Dumble, and the Trainwreck). Any further suggestions ?
I think it's a great idea. Several heads and a couple of different cabs. The heads I've built so far sound great.
But that's me. If you had to buy an amp for each voicing, that would be very costly very soon. IN this respect, a modeller would be great.