I really don't think you should have both resistance and signets on the cards. If you do that for one character, you're locking yourself into doing it for everybody, because at that point you'll have to stay universally-consistent on where the strength boosters are on weapons. Changing the strength icon to another circle isn't really a big deal, but I do feel like you lose a degree of flavor.
Now, for some additional options:
1) Overlay signets and resistance. I think we can all agree that resistance should be a stat given to every companion, and that signets wont always be required. So why not put a signet icon behind the resistance number when they do appear?
2) Different-colored resistance. Each color would represent a specific signet - a silver resistance would be Aragorn, pink for Theoden, tan for Gandalf, green for Frodo. Again, you're sacrificing the flavor of actually seeing the signet in order to keep both signets and resistance, but it would work.
3) Ditch signets. I think nostalgia has more to do with our desire to hold onto signets than real gameplay value. Very few cards played off of signets, and most that did offered very little to competitive formats. I always bring my points back to flavor: signets might look nicer than resistance, but on most characters they seem randomly assigned, while resistance usually makes sense at all times.