You almost sound like you have been there. If VN announced free elections for a parliament and president to take place in 6 months, yes, the current crowd would probably mostly still be in power but they would be in a new situation and would find that they would have to be responsive to the voters rather than the committees. If democracy is accompanied by extensive market rationalization and reform the corruption will subside drastically. Market reform and ending government interference in the market is the key. Divesting the banks, if it is real and not just for show, is a major first step.
If Vietnam were so bold as to create a six month plan, I would not expect it to succeed. The revolutionary democracy you propose would most likely only take root in a country utterly devastated, like Iraq. Otherwise, the people would likely not support it.
The assumption has to be that while change is needed, there is a strong fear of chaos and violence. This is abhored by everyone, which creates a feeling of hesitation, of inertia, against change. For this reason, small steps as confidence building measures are far more likely to result in a peaceful evolution to democracy.
Openness and the absence of corruption would take many years to develop, even after democracy.