Spell-Forwarding is a rare thing to find. I believe CC-Target has the option both with friendly-to-hostile and hostile-to-friendly spell forwarding. However, I'm not interested in running the core CC mod.
I've been looking at the options for a long time for my own use; I'm pretty new to lua and I've been trying to decide what the best way to approach this is. I may never get around to it, so if somebody was interested in writing a simple spell-forwarding mod that would be great.