It's an extension of the political reforms instigated by Diaz-Canel's predecessor, Raul Castro, the brother of revolutionary icon Fidel Castro who led the country from 1959 and the toppling of the Batista dictatorship until 2008.
Since taking over from his brother, who died in 2016, Raul Castro pushed through reforms that allowed private initiative and now almost 600,000 people -- 13 percent of the workforce -- are employed in private enterprise.
"That the market takes on greater importance was expected," constitutional attorney Jose Antonio Fernandez told AFP, predicting it would increasingly play a role in Cuba's economic and social policy.
The draft of 224 articles, prepared by a parliamentary committee headed by Castro and Diaz-Canel, will be voted on by the National Assembly before being submitted to a popular vote.
Foreign investment will be recognized as an important spur to development, according to details of the document published last Saturday by the official newspaper Granma.
It will also allow for the legalization of small and medium-sized businesses.
Changes had already been afoot with the issuing of new business licenses restarting last week after a year-long hiatus sparked by fears over the accumulation of personal wealth.
"I hope the constitution limits the market, so that the market sparks development in the country without stifling the humanist character of the revolution," said Fernandez.
Other changes will see the name of the country's head of state reverting to "president of the republic" instead of the name given since the constitution of 1976: president of the council of state.
Democratic elections are not on the table and the president will still be elected from amongst deputies in the National Assembly, the "state's organ of supreme power."
But a new position of prime minister will be created for the first time since 1976 -- which Fernandez suggested could be a step towards taking away executive and administrative responsibilities from the president.
"It could help to balance out the issue of the concentration of powers," he said.
Further changes will see a provision inserted guaranteeing the right not to face discrimination over gender identity.
After the 1959 revolution, Cuba was a hostile place for the LGBT community, although in 2010 Fidel Castro did admit responsibility for "injustices" perpetrated against homosexuals.
But while employment discrimination based on sexual orientation is banned, same-sex civil unions have remained off limits.
"I hope that the family chapter, which is totally heterosexual in its concept, opens the door to equality in marriage and adoption," said Fernandez.
Some freedoms will be harder to win, though, despite the new constitution recognizing Cuba as a democratic, independent, sovereign socialist state governed by the rule of law.
"Recognition in 2018 that Cuba is a state governed by the rule of law is a tremendous victory for democracy," said Fernandez.
"But that needs to be followed by (changes to) laws and the Cuban legal system."
Among those, he says, are "the regulation of political and social relationships, human rights guarantees, freedom of the press, speech and thought."
Press freedom is one area in particular where Cuba is severely lacking.
US government-funded democracy and human rights watchdog Freedom House ranks the country's press as "Not Free", giving it a score of 91/100 -- with 0 being the most free.
"Cuba has the most repressive media environment in the Americas," it said in its 2017 report, noting that while independent press is "illegal, yet tolerated," although only if exercising high levels of self-censorship.
In a recent speech at a journalists' congress, Diaz-Canel criticized reporters working outside of official state media, and left no doubt that constitutional changes did not mean ideological ones.
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