Can shemitta be re-instated in modern day Israel without radically altering the rabbinic understanding of the institution?
The Jewish people could do a Gorbachev on shemitta and just fiddle with it around the edges before the institution collapses under its own weight and its own contradictions or the Jews could admit that ChZl just had it wrong, that modern day science and politics understand the deeper structures of the sabbatical institution more clearly and more technically now than they could have back then. Jews would then proceed to repudiate as failed and defunct the methodology and the shape ChZl had originally designed for shemitta.
Instead, Jews would take out a blank sheet of paper and start all over again with a practicable version of shemitta that doesn't take so many liberties with the text-as-written but which focuses on the deeper, though more mundane application of the system beginning with a voluntary collectivism that would limit membership to those who contributed to the storehouses of shemitta during the prior six years.
The Jewish people wouldn't even necessarily call it shemitta. They would instead all engage in the heter machira but would proceed to build the storehouses and assemble as broad a membership as possible for what we would call The Sheviit Project.
The Sheviit Project would be the next generation of the kibbutz movement. It would be a voluntary membership in a collective style of living. Those who chose to join would participate in the benefits of the collective. Those who elected not to join could not participate in this more essential kind of shemitta.
It's not clear why the people of Israel couldn't live side by side with those who joined this mutual fund/mutual assurance society/mutual aid society entering into contractual obligation with each other that was governed by the rules of The Sheviit Project in much the same way as the Chumash devises mutual obligations to those it calls one's brothers and one's comrades.