Transhumanism: at what margin?

I tend to sympathize with transhumanist ideals, if only for the same reason that I do not hesitate to use antibiotics.  Furthermore I have never had huge hang-ups over the "identity" concept; I don't celebrate St. Patrick's Day and I find it embarrassing to admit that I root for the Washington Wizards.  "The Six Million Dollar Man" was one of my favorite TV shows as a kid, although even then I thought the price was too low.

That being said, the economist in me asks not "whether" but rather "at what margin"?  Is there any margin at which concerns of identity should cause us to reject otherwise beneficial transhumanist improvements?

Most people want their children to look like themselves, and to some extent to think like themselves.  We invest many thousands of dollars and many months of our time to acculturate our children.  Now let's say your children could be one percent happier throughout their lives, but this would mean they were totally unlike you, the parent.  In fact your children would be turned into highly intelligent velociraptors and flown to another planet to live among their own kind.  How many of us would choose this option?  I can think of a few responses:

1. Transhumanism will bring improvements of more than one percent; we should forget about identity and let everyone become healthier and happier.  What's wrong with uploads?

2. Governments should not restrict transhumanist innovation.  Let people and their children choose their degrees of identity continuity for themselves.  (Isn't there a collective action problem here?  Everyone wants a more competitive kid but at the end humanity is very different.)

3. The parental analogy is not relevant for policy choices.  Parents should be partial across identities, but governments should be more neutral.  And surely uploads will still be allowed to vote, no?

4. Identity attachments are, very often, petty and small-minded to considerable degree.  We should be cosmopolitan across chimpanzees and intelligent velociraptors, not to mention enhanced humans.

I still favor laissez-faire for transhumanist innovation.  And all the listed arguments have force with me.  But I would feel better rejecting the critics if I had a framework that would simultaneously recognize the value of identity while giving it limited weight to override medical progress.

These thoughts were stimulated by reading the new and useful More than Human: Embracing the Promise of Biological Enhancement, by Ramez Naam.

Addendum: Here is an excellent Nick Bostrom essay, which argues human evolution may otherwise deteriorate.  He also wonders whether happiness and consciousness have evolutionary advantages in the long run.  Thanks to the Vassar family for the pointer.