Babyeater babies don't want to be eaten, or particularly want to eat their peers, and those who will never develop a desire to eat babies constitute a majority of the sapient population at any given time,

Using the observation that being dead precludes wanting to (and endorsing) eating babies as an adult as a technical reason that "those who will never develop a desire to eat babies constitute a majority of the sapient population at any given time" is highly misleading. I'd go as far as to call it bullshit.

We could equally as accurately say "those who will never develop into non-paperclipping adults constitute a majority of the sapient population at any given time" (therefore CEV<Babyeaters> means paperclipping!)

so "eat babies" isn't the 'coherent' part of the babyeater CEV.

Any attempted implementation of CEV<Babyeaters> that does not result in the eating of babies sounds like a catastrophic failure. It would seem to result in the sneaking in of non-babyeater values at every excuse.