Many witnesses create a new account for their witness (so their blog/main account is separate form their witness/alt account). The rep can be circumvented (and augmented) by one or two high-rep/high SP accounts.. so while the timing of the puppet accounts' rise to witness may take a little longer, it's still possible to bypass such a limitation.

Regardless, the best part about a blockchain is that anyone can be a witness with enough support from the "community".. limiting by rep is an arbitrary barrier to entry that may make potential adopters shy away from the "eliteist" protocol/restriction on becoming a witness..

Just my $0.02