In Fig. 26.16 can't we remove the φ2 switches on the bottom of C2 for
better operation? Won't keeping those switches create an error in the
output common-mode voltage?
The problem with removing those φ2-controlled switches is that then there
isn't a DC path to VCMFB. VCMFB is only connected to capacitors or the gates
of MOSFETs (so its initial value is unknown and uncontrollable).
Yes, there will be an offset in the output common-mode voltage. This offset,
as discussed on page 875 is set by difference between the ideal VCMFB and the
actual VCMFB. In Fig. 26.16 the ideal VCMFB is Vbiasn.