(I previously posted this answer on travel.SE but the question was closed there)
As you hinted in your question, the J-1 transfer regulations (22 CFR 62.42) are not entirely clear as they do not directly address the question of being outside the US during a transfer. There are some practical problems involved, such as the requirement for the new program sponsor to immediately validate your program which includes confirming your "actual and current US address". The Responsible Officers of both the old and new program sponsor have some discretion in determining what is acceptable, so the bottom line is you can only do it if both of them accept your plan.
If possible, you could avoid such issues if you can be in the US to continue participating in your current J-1 program first, and then do the transfer within the US. Alternatively, if you don't plan to enter the US at all, you might not need to maintain J-1 status at all.