If you are in VMC you cancel IFR
Do any airlines currently permit flights to cancel IFR?
If we upgrade to class E
VFR:
Continuous 2 way communications required.
Transponder required.
Many sport aviation types as well as gliders have exemptions from both to operate in Class E. They have done for many years, and regularly operate in Class E.
Presumably ATC would have no awareness of such aircraft, if they can't see them and/or can't talk to them.
If these exemptions are going to be pulled, the SAAA/RAA etc. might have something to say.