It may possibly fix the outflow to the seabed if the relief well intended plugging can be successfully place below casing that is damage. It is still questionable whether the bottom kill will work as intended due to a lot of mitigating factors. The BP stupid top kill probably is to blame for aggravating the damage to the casing during the initial explosion. IMHO
I'm not an expert but I have common sense, I guess the best solution is just to continue with the retrieval through the new cap and use the relief to do the same as well rather than use it for bottom kill which maybe an exercise of futility.