I agree with most of what you say.But for the general population OCI is sufficient without having the rigmorales of dual citizenship and consequent legal issues of consular protection.
There are also some of the points you mentioned that I need to clarify (corresponding to your points):
2.The act granting OCI and Indian citizenship are the same.Technically if OCI is vulnerable as you say so is Indian citizenship.I know citizenship is a constitutionally garunteed right but if they enter some weird amendment as a prerequisite for citizenship (say 5 years of military service) you can be denied Indian citizenship as well (This is of course a long shot).
3.For visiting PAP/RAP areas Indian citizens too need to apply to the army for a permit.I dont think there are any other areas that OCI's are denied access t
4.A child of an OCI can claim Indian citizenship by birth if he fulfils the provisions of the Citizenship act.If a person is eligible for OCI (in the current generation atleast) his child would also be eligible for OCI.The naturalisation route is always open.
7.An Indian citizen does need to maintain an Indian passport
.BUt this problem would also exist if there was dual citizenship as well.This is not an OCI specific problem
8.An OCI holder can avail of the tax treaties just as an Indian citizen can.
In my personal opinion OCI is suitable for a majority of the PIO population.It offers substantial benefits and also makes the path to full Indian citizenship easier.
As far as the voting issue goes,well, i would prefer to be a voice in my country of residence.It would be unfair to the citizens of India if a person sitting in another country can be an influence to decisions that affect him on a daily basis.This of course is my opinion.If i want to vote in India I will give up my foreign citizenship and become a full Indian citizen first.
As a footnote I would like to mention that OCI is a roll back from the previously promised dual citizenship and is probably the result of some babu flexing his muscles.But in the final analysis OCI is a step forward and is not bad.