I have a doubt that F-7BGI is capable enough to replace these super-capable (in its class) deep penetration attack aircraft. These are legends. Even PLAAF has not found any suitable replacement for these.
F-7 is not a multi-role deep penetration plane like Mig-29. It is basically a bomber with functions also of a fighter. I have heard that BGI is F-7 only in name. Its design is completely different. If it is true then there is reason to believe that BAF is deceiving its neighbours. However, even if it is a normal BGI without a deep penetration capability BGIs from Cox's Bazaar base will certainly be able to bomb nearby targets in Sittwe and other military assets of Burma.