Well let me say, if SYS A has failed then FIRST you should not put the gear dn until you a very sure of a landing.
Second, now if you have further bad luck and have to go around, on 2 engines with the gear dn, its not so critical. The aircraft will still climb to above the lowest safe in any case.
Now if engine 1 failes in the climb, you can retract the gear.
If its NOT your day, and engine 2 fails, then there is no way of retracting the gear.
My advice as a Captain on the B737 is: if after go-around, you still have plenty of EXTRA FUEL, then dont touch anything. ( Dont play around with CBs and shuting down engines, for various reasons), just continue to your closest ALT where the weather is good, with the gear dn and 2 engines running, especially if the ALT is very close by.