in your mind (mine as well) it sounds like a great idea. but in reality, it's VERY difficult to pull off. the "sound" becomes too "fat" and it just doesn't work out most of the time. i briefly experimented with this idea many years ago with a project called "the mountain band". we had 5 guitarists, 2 bass players, 2 drummers, and 5 singers. it was a nightmare for the sound guy, let alone everyone else. it has been done effectively but it's really tough to pull off.
speaking of strings, one of the reasons i love the twelve girl band so much is because they play a blend of folk, modern, and classical, and chinese, but with traditional chinese instruments that go back more than a thousand years. so it's classical, but yet it's not. it's rock, (some of it) but it's not. it's "ethnic", but in more than one way. that, and the skill involved is monumental. i would love to try this piece with all guitars: