1. if building does not have OC then bear in mind that all the taxes like property, water, etc. will be charged at higher rates by the municipality
2. there are many buildings in Mumbai and suburbs which do not have OC and people buy such properties and begin to live in it for years without any problems, but u never know
3. so it is a risk which you will take
4. if you have come for an advice, then it will be a NO
5. also consider from the future point of view when you go to sell this flat. What if by that time the OC is still not received? will you be able to find buyers?
6. the modification in carpet area will obviously create legal issues for the OC. For grant of OC, the local body will do an assessment and inspection of the building to check if there are any violations of FSI and sanctioned plans. If they find any such deviations then the OC will be stuck. However the local bodies are very corrupt and may even demand illegal gratification or ghoos to let go such deviations. So carpet area deviation from sanctioned plans must not be there, particularly when the OC is not received
7. another angle to look at the issue is from redevelopment point of view. When a builder approaches the society, he will have an upper hand as he can say that as he has incur expenses for getting OC issue cleared, he will not be able to give the redevelopment benefits as are being demanded by society members. As opposed to that if everything is clear then clearly the society and its members will have an upper hand while negotiating with builder
8. also if you are planning to take a bank loan, the bank may refuse to sanction loan if the building is without OC
9. So its a calculated risk which you have to take considering the above