[Irrelevant]

I think it is rather unfair on someone who just did a close-range super (BB X, Super Hundred Kick, etc) to have it smashed by a Hadoken/Sentinel Beam etc.

I think it would be fairer if someone doing a super (the attacking part of them anyway) was immune to normal attacks & combos.

For example, Chun-Li has just done a Super Hundred Kick, & is aproaching Ryu. Currently, Ryu could just Hadoken her, & cancel the super. With this implemented, Chun-Li's fast-moving leg would absorb the impact without the super being cancelled, & with little or no damage. Ryu would, however, be able to jump over Chun-Li & attack her from behind without problems.
The same would apply for a Sentinel Beam. From the front, Chun-Li's attack would act as a block, but from behind, she would still be vulnerable.