Qualification for Welfare Officer under FA is not generally BSW / MSW. It is depends upon the State rules in this regards.
You need to see the rules in this regards as framed by appropriate Govt. of you.
In Maharashtra, to qualify for this post one has to give viva-voce test and get himself enrolled in the list maintained by Labour Department. Disqualifications also are mentioned in the rules.
Notification under the Maharashtra rules in regards to qualification of degrees / diplomas, has listed as many as 20 and more such degrees / diplomas as recognied, to my knowledge.