Mike Mushok from Staind doesn't use 7-strings. He uses extra-long scale 6-strings, and lots of us have already mentioned how much we'd love to see that as a production model.
Wes Borland used Ibanez guitars because he was dirt poor they gave him free guitars after the guys from Korn hooked him up. He has regularly said he wanted to become a better player with a 6-string.
Personally, i don't think Ibanez needs more signature models, and especially not ones that are just tweaked variants of the RG line. What they need is just more variety in the lineup, or some kind of basic build-to-order system for us regular folk. Not quite a custom shop, but a few options that could be assembled fairly easily would be nice.