Dear all,
I've recently messaged InsanitySorrow about using his assets from his many amazing mods, not only for Skyblivion, but for a personal Overhaul as well.
He has denied permissions on both counts. I consider this an official answer (as he indicated that other people have approached him and received the same response), and thought I'd best share this information so no-one else bothers him.
Shame, but there you go.

You should have asked first,
You should have asked first, it is well known fact that he didn't gave permission.
This is also the same for any mod makers from such sites TES Alliance as Dark Creations. They don't support Morroblivion projects for obvious reasons.
By the way, why you are even searching for replacers? Skyblivion (I hope) will use ported models for everything in base installation. Any other replacers are optional and can be done via plugins as ordinary mods. Don't forget you can mod Skyblivion like a separate game.