It is surely permissible, and in that sense "acceptable", to propose changes, even fundamental changes, to laws and legal systems. In that sense the answer must be "Yes, it is acceptable".
But as I understand the question, that is not what is being asked here. The OP is asking whether such proposals are part of the mainstream discussion or are on the legal fringe. That is harder to answer.
There is a long tradition of using or proposing to use "Natural Law" to determine what statute or constitutional law should say, or to help decide the outcome of individual cases. My understanding is that in the Anglo-american legal system, that position was more favored during the 1800s and early 1900s than it is now, Some judges, and indeed some US Supreme Court Justices, cited Natural law directly in some opinions. Others assumed views similar to Natural law, without using that term.
Indeed many of the "fundamental Human Rights" were derived, at least in part, from a natural law perspective.
In THE U.S. SUPREME COURT and NATURAL LAW (2011) by
Paul Moreno, of Hillsdale College, the author writes:
The United States Supreme Court has been reluctant to argue from universal principles not announced in the Constitution’s text, or at least to do so in an articulate and systematic fashion. It has preferred to limit itself to the text of the Constitution, statutes, or treaties, wary of going beyond these texts or the intent of their framers and ratifiers. Nevertheless, the Court has on many occasions engaged in a variety of natural-law analyses.
In the broadest sense, “natural-law jurisprudence” involves a judge’s resort to a “higher law,” one anterior and superior to the written constitution. The ancient Athenians, for example, distinguished between man-made laws (thesmos) and natural laws (nomoi). The Romans, particularly Cicero, similarly argued that human law ought to be in conformity with eternal principles of “right reason.” The Institutes of the Emperor Justinian noted that slavery existed by human law but was contrary to nature. A great revival of natural law thinking took place in the high middle ages, particularly in the work of St. Thomas Aquinas. English jurists, particularly Bracton and Glanville, maintained natural law theory, distinguishing between the natural rights of the subject (jurisdictio) and the power of the government (gubernaculum).
The notion of natural law pervaded the period of the American founding. It was expressed in the Declaration of Independence’s claims of “self-evident truths” about human equality, the necessity of consent, and the right to revolution. The idea of natural law was prevalent at the Constitutional Convention and during the ratification debates, though not so much in the text of the Constitution itself. William Blackstone’s Commentaries on the Law of England (1765–69), a widely-read treatise in the American colonies, contained one typical expression of the idea of natural law. James Wilson, a delegate at the Convention, important Federalist defender of the Constitution, and Supreme Court justice, made many natural-law-based assumptions in his celebrated law lectures given at the College of Philadelphia (1790–91).
Decisions of the early Supreme Court were often forthrightly based on natural-law arguments. In Chisholm v. Georgia (1793), for example, Justice Wilson held that a South Carolina citizen could sue the state of Georgia, not just because Article III of the Constitution gave the federal courts jurisdiction in “controversies between a state and citizens of another state,” but because of what he believed to be the “principles of general jurisprudence” upon which the Constitution rested. (The decision was ultimately overturned by the Eleventh Amendment in 1795.) In the same term, the Court, interpreting both the federal and state constitutions, noted that “the right of trial by jury is a fundamental law, made sacred by the Constitution,” and that “the right of acquiring and possessing property, and having it protected, is one of the natural, inherent rights of man” (Vanhorne’s Lessee v. Dorrance). Justice Samuel Chase gave a fuller statement of a kind of natural law theory in Calder v. Bull (1798).
The purposes for which men enter into society will determine the nature and terms of the social compact. . . . This fundamental principle flows from the very nature of our free republican governments. . . . There are certain vital principles in our free republican governments, which will determine and overrule an apparent and flagrant abuse of legislative power. . . . An act of the legislature (for I cannot call it a law) contrary to the great first principles of the social compact, cannot be considered a rightful exercise of legislative authority.
Chase gave as examples “a law that makes a man a judge in his own cause, or a law that takes property from A and gives it to B.” “It is against all reason and justice, for a people to entrust a legislature with such powers; and, therefore, it cannot be presumed that they have done it.” Justice Chase, an ardent Federalist and judicial activist, became more restrained after he was impeached and nearly removed when the Jeffersonian Republicans took over the government in 1801.
Something of a retreat from natural-law-based jurisprudence in the Court’s opinions is evident in the early nineteenth century. In part this retreat was a reaction to the excesses of the French Revolution, which began with intense assertions of the “rights of man.” It also reflected the Jeffersonian and Jacksonian democratic suspicion of natural law as the province of elite lawyers and judges. Thus Chief Justice John Marshall usually preferred to base his decisions only on the Constitution’s text rather than to appeal to principles of natural law found beyond the Constitution. In Fletcher v. Peck (1810), for example, he did refer to “the principles which are common to our free institutions”—the “vested rights” of a property owner, as Chase had described them. But he primarily appealed to “the particular provisions of the Constitution”—in this case, Article I, section 10, the “contract clause.”
So there is long precedent for assertions of Natural Law, and for using natural law concepts and theories in deciding legal cases. But, at least in the US, this precedent has been much less followed in the last century and more.
I am not as knowledgeable about the place of natural law in European civil law systems, and in academic theories of law in European, particularly eastern European countries. I cannot really say how much the main thrust of such discussion favors a Natural Law analysis at present.
The traditions of academic law are not really the same as those of the natural sciences (now sometimes called just "science"). The strong scientific tradition of openness to "innovations and discussions" is not as strongly marked in legal academic thought, nor in judicial opinions, to the best of my understanding. But Natural law is not a new theory in academic legal circles.
One should note that there are many flavors of natural law, which come to quite different conclusions on various points. Not all versions of Natural Law theory may be equally in fashion in any given academic community.