Reconstruction issues

In Chennai, my flat is 30 years old and there are 8 units, of which 2 owners are ready to spend money on constructing their own apartment because they will now get a bigger house as the FSI is 2 vs it was less 30 years back. Rest of the 6 are either not willing to spend on the own construction cost or not financially sound. But If I give it to the builder, I will get the same size house with reduced UDS which the 2 owners are not willing to. How to deal in this situation.