How low do you actually want to go?
I actually might not want to go that low. I think the lowest will be B (but I'll probably stay go with C and C# most of the time) and as far as I know 24,75 scale lenght guitars can manage this. Or am I wrong?
I wouldnt advise it. It is doable but not optimal. At the minimum id use a 25.5 for that.
The RGD that i mentioned has a native tuning of D standard/Drop C so i reckon that will be optimal for you.
I think there are a few schecters with 26.5" scales too
Thing is I'm not to keen on the Ibby design or pointy guitars in usual :?
Doesn't In Flames use Gibsons in very low tunings?
I'm rather of the view that if 56s on a Les Paul are good enough for Bill Steer to use on Heartwork, they're theoretically fine for anyone, and the only reason not to do it comes down to personal preference.
I use 12-56s on my Gibson V in my band where I'm tuned down to C# (sometimes drop B) and, since a setup from Jonathan at Feline, it's been absolutely fine for me (seem to remember he had to flip one of the saddles on the bridge round to get it to intonate ok, but that's no biggie as far as I'm concerned). That said, I do like a bit of give in my strings, so if you're used to much higher tension, I can see how it may feel a bit flappy.