Over the years, one thing I've noticed about the Undertaker is that he doesn't really seem to be about championships. He is one of the most feared, respected, and unique individuals to step into a WWE ring and it's not his title wins that make him this, it's the fact that he is a locker-room leader, he is loyal to his fan-base, and he is a true entertainer. His gimmick has survived all of the WWE's eras and it constantly evolves to stay fresh.
I honestly feel that 'taker wouldn't want the IC Belt, not only because he isn't about championships, but I think he'd rather see it on a younger guy to help with his push. I think someone like Cody Rhodes carrying the belt is perfect. The guy holding the belt doesn't need to be a legend, but if he faced top tier talent and constantly retained, wouldn't that give credibility to the belt as well as Rhodes?
For instance, have Rhodes interact more and more with HHH calling him out on things, and then have HHH stick him in more high profile matches with his belt on the line to punish him, but have Cody retain at all costs, proving how much his IC Belt means to him. Hell, him just mentioning the past greats that held it and reverting back to the old title belt, to me, restores some of it's prestige.