I agree with all the points except that u said Iran is not big .I agree with Shirvan that this announcement might be a hoax or a half-baked initiative.
1. China doesn't have good track record on following through with its mega projects.
The much advertised Nicaragua Canal project did not materialize. Pakistan is disappointed with the way Chinese projects are turning out and increasingly shifting toward Turkey. Many African and Asian developing countries are rethinking their agreements with China on the Belt and Road initiative as it results in countries being in unbearable debts and giving up the control of their resources to China.
2. China is not stupid and knows Iran is not the kind of a country it can bully and extract concessions from. Iran has rich history and is very similar to Turkey in self-respect. In Turkey, China invested in railroads and other infrastructure projects under the Belt and Road initiative but failed to gain influence. Iran won't be any different. Why would China dump $400 billions in such a country?
3. Iran can only benefit from the proposed project if China buys Iranian oil and gas. The reality is the US is far more important for China as an economic partner than Iran. China basically stopped buying the Iranian oil when Trump instituted the sanctions against Iran. It is unlikely to change.
4. Iran as a manufacturing hub is only good for its domestic market as Iran is not big and deprived of in participating in international trade of consumer goods. Iranian market is too small for this magnitude of investment as its population doesn't have sizeable purchasing power. Surely China is not gonna make goods in Iran and export them back to China.
5. The Chinese base in Iran is a pipe dream. Iran will not allow a full-fledged foreign base on its territory. Russia and Turkey tried once and came out of it empty-handed.
I am pretty sure there many other points to be made for and against the feasibility of the pact. I just pointed out few that came to my mind. I didn't talk about Israel on purpose as to not complicate my points even further, but I am aware.
Pakistani nuclear program was assisted by China to keep the region more balanced when India went nuclear.On the other hand China's closeness to Pakistan is for the most part to contain Indian influence in south Asia uno
Chinese companies badly need access to the Western capital markets as China itself is drowning in debt. To sustain growth, they need to have access to the US and the EU as these two are China's biggest trading partners. Since the dollar is the de facto world currency, China will not risk its ties with the US over Iran.On the other hand,the Chinese are no longer interested in appeasing the US by not purchasing the Iranian oil because Washington is not showing any sign of ceasing their cold war with China.