What about using the voice of Dean Erickson, who was Gabriel in GK2? The character sketch for Gabriel for the remake certainly resembles him. From his webpage athttp://deanerickson.com/
it looks like he's not in acting any more. But who knows, he might enjoy reprising his role as Gabriel.
It sounds like Tim Curry is recovering, but maybe not enough to do the voice acting yet. I hope he makes a full recovery. I'd assumed he was too much in demand to do Gabriel, though that may not be the reason.
Edit -- That's good news, Rushes.