When you say gale sail, I assume you are referring to the storm sail of that name that fastens around a furled genoa/jib and is hoisted with a separate halyard using the rolled genoa as the stay.
Though there are some clear advantages to a hanked on
jib on a separate forestay if you have somewhere suitable to mount it, you might want to balance the tradeoffs of convenience and effort a little differently and go with a gale sail. When you don't need it, the gale sail is certainly easier to store than the additional forestay.
I have a gale sail on my cat as a storm sail, but have only rigged it in benign conditions so far so can't say how well it will really work in nasty
weather, but from it's design I'd say there is a good chance. Remember that whatever you are
rigging in those conditions, you do have the advantage of a large level platform to work from.
Mark.