The Soviet Union tried that. You can see the results. Expansion of NATO into those areas and attempts to finance insurrections inside the remaining Russian Federation like in Chechnya, direct funding of paid opposition like Navalny, and mass protests. Meddling in elections like the funding given to Yeltsin to continue the robber barons free hand into plundering Russia's natural resources so they can be sold to the West for peanuts.
One thing that I truly appreciate a ton lot is how China did not follow the Soviet way of managing administrative divisions within the country.
Like seriously, not even the preceeding Russian Tsarist Empire has ever allowed the kind of automony at higher levels of the regional governance as much as the Soviet Union did with their respective Soviet Socialist Republics (SSRs). Setting up those SSRs and leaving the entire union as some kind of grouping of federations of republics with their own system of communist party and government, rather than attempting to gradually absorbing and integrating them proved to be a recepie for disaster.
For instance, you even have divisions in the Red Army according to their respective SSRs, such as the Belarussian Front Armies, Ukrainian Front Armies, Georgian Front Armies, Armenian Front Armies, etc in the Great Patriotic War.
As soon as Moscow is headed by one who is both incompetent and easily swayed by malign foreign influences to loosen central control over the Soviet Union, the dissolution and disintegration of the entire union is just a matter of time. This eventually became a reality when Gorbachev kickstarted the decentralization of the union, and you can already see how quickly elements vying for independence sprang up across those SSRs like mushrooms. Coupled with Western support for these elements in these respective SSRs (Ukraine and the Baltic states are prime example of this), and the rest is history.
What Mao's China definitely did right is centralizing significant portions of the governance of the country in Beijing. Even for autonomous regions, they all would still have to rely on Beijing on major issues like security, defense and certain local policies. This meant that even if there are elements of seperatism and extremism that pops up in those autonomous regions, they got immediately crushed by Beijing.
Imagine the new China in 1950 under Mao decided to adopt similar administrative divisions for China as the Soviet Union, i.e. Union of Chinese Socialist Republics (UCSR), and then designate autonomous regions as Chinese Socialist Republics, or CSRs. You would have:
1. Tibetan CSR, capital Lhasa, headed by the Communist Party of Tibet as a branch of the CPC;
2. Inner Mongolia CSR, capital Hohhot, headed by the Communist Party of Inner Mongolia as a branch of the CPC;
3. Xinjiang CSR, capital Urumqi, headed by the Communist Party of Xinjiang as a branch of the CPC;
4. Guangxi CSR, capital Nanning, headed by the Communist Party of Guangxi as a branch of the CPC; and
5. Ningxia CSR, capital Yinchuan, headed by the Communist Party of Ningxia as a branch of the CPC.
Seeing how the US-led West and India have been proactively backing and supporting seperatism and extremism in Tibet, Xinjiang and Hong Kong, imagine how things would have gone differently had China followed the Soviet Union.
