I prefer not to consider this an option, but maybe others feel differently. Therefore the restriction of C to scalar lvalues must be considered a fundamental one. Fortunately, this restriction is not a problematic one. For example, arrays and hashes can only contain scalars, and nobody has ever considered that a problem. Frozen after some discussions on the mailing list.
People seem to be divided in two groups.
One group considers an lvalue return solely for assignment, and hence propose to add an additional magical parameter to lvalue routines. Other RFCs deal with that approach. The other group joins me in the opinion that lvalue means, in essence, equivalence to a variable. This RFC is for them. Clarified the syntactic sugar misconception.