A new draft. If we move the individual shooting factors up to be 3, 4, or 5 instead of 1, 2, or 3 we get a table like this. Now, with the addition of the roll of four FUDGE dice we get a much more palatable result range. It does involve potentially counting up lots of numbers, but these numbers will only ever be 3, 4, or 5. And having said that, while you might have 15 musketeers crammed into one square, it is more likely that you will only ever have five or six.
Click this link to see the new table: more-escarmouche-firing-factors-2.pdf