Complementizers as heads in the GM

I think I’ve asked this before but I cannot locate the email, so I will ask here:

What is behind the decision to not use P&S’s analysis of complementizers as markers? (And treating them as heads instead).

Here’s P&S’s motivation for their analysis of complementizers, which in the book are markers (a special thing they introduce for this purpose). (I will say upfront that I did not like this motivation that much.)

  1. GB traditionally sees them as heads but GB’s motivation depend on GB-internal assumptions (may be true, but is not a motivation of the alternative per se).

  2. Verbs subcategorize for different forms of sentential complements.

They do not discuss why they wouldn’t want complementizers to expose their complement’s FORM. Perhaps they want FORM to be strictly a verb feature?

I haven’t checked the book to see, but I’ve never much liked the head-marker analysis either. It seems to add complexity (additional rule types) with relatively little gain (not needing to copy certain head features from e.g. the S to the C).