This one might be easy...how about a version where the 5 original modes still match up with their chosen songs, and the other songs are replaced by late 60s stuff - the background songs, the wizard modes and match songs etc.
Would fit the Beatlemania theme better, as well as fit with the cousin brucie clips better and the songs won't fade out and restart as awkwardly during modes, but still give you a taste of the stuff we all want (the later stuff). And the inserts would still match up with the songs, though that isn't really a big deal for me. Would make for a diverse game representing both eras.
I don't think most beatles fans really prefer one over the other. I never really listed to that stuff even though I recognized it was good and catchy. Part of the game that has been fun is really listening to that old stuff and seeing the quality of it. I don't think I'd ever even heard It Won't Be Long, cool song.