The Helldiver's timing problem

If the SB2C Helldiver had entered service as a later variant, how many additional modifications would the Navy want?

It would depend on the circumstances, because the deeper problem was that the specialized dive-bomber role was already declining.

No universal modification package is offered because the answer depends on the circumstances of service entry. The SB2C Helldiver's larger problem was timing rather than a single missing technical fix. By the time the aircraft matured, navies were beginning to move away from specialized dive bombers. Further modifications would have to justify themselves against a role that was already declining.