Fascinating! My actual thoughts on this were along the same lines- that shaving the center was meant to represent or facilitate a direct connection with the Holy Spirit. I thought perhaps Jewish people wore skullcaps as they believed the savior had yet to come. There is a definite correlation, and I wonder if one of these religions did this in direct answer to the other.
Interesting sidenote: The Roman Catholics abolished the practice of shaving the center- or tonsure- in 1972. I can't find the reason for that, it simply says that certain orders of monks etc. with papal permission can still do it, and while there was no official comment on why, it was assumed to be a vanity issue, that they were worried less young men were studying the priesthood because of it. (I don't believe that though, definitely more to it)