I find it pretty disappointing that SICP is considered too tough for matriculants of a top CS program. Perhaps you should consider enrolling fewer students and raising standards.
I'm haven't said that, so please don't insult my students by saying that. My argument for it being a capstone stems not at all from that it's too hard. We can not, should not require our students to be putting in the amount of time necessary, in my opinion 40hrs/week, to completely 100% understand this material as a freshman. In my mind, completely understanding it is required for the 'enlightenment' that many like about SICP, but this is not true for many other courses. By putting it in Python, students can learn many useful skills along the way.
Furthermore, I'm arguing that all things being equal, the time is better spent as a senior when you might be able to get the same points for a much lower time commitment.
And, please, remember that this is just one class in a curriculum of CS courses. There is a lot of effort being put in by dozens of professors to graduate the best and brightest, which we do.