The problem I have with confessionalism can be summarized in two words: locality and constitutionality. I don't have difficulty with confessions of faith, per se. But we must recognize them as limited by their local nature (i.e., they are not universal), local context (i.e., they address issues at hand at a particular time and in a particular setting) and local perspective (i.e., they cannot anticipate later developments, broadening horizens, or new circumstances). This is particularly problematic when a church or tradition affirms a confession as constitutive of its life and existence, where a confession stands as the unalterable sine qua non of "true" Christian faith and practice.
GAFCON's "confessional Anglican" alternative shifts the balance between "catholic" and "reformed" that presently characterizes Anglicanism dramatically to one side (i.e., the reformed). Hence, the suppression of those Anglicans out of sync with the confessional rationale is inevitable, IMO. This is not a good scenario for catholics. Just ask Jim Packer.