Every additional character participating in a SF always extends the range by 1u, regardless of the type of weapon used. MG counts as a single characters on their own, thus 1 character + MG is the same as 2 characters with light infantry weapons.
SF range becomes always the same for everything: 2 characters or 1 mg (1 crew)= 3u 3 characters or 1Mg (2 crew = 4u 1 characters + 1Mg (1 crew) = 4u 4 characters or 1Mg + 3 crew = 5u 1 characters + 1Mg (2 crew) = 5u 2 characters + 1Mg (1 crew) = 5u etc.
We have recently started experimenting with this, it give additional scope for adding extra infantry fire in a SF area once established (currently the only benefit is an extra dice roll for random ricochet hits at the beginning of the turn), it's realistic and also balance things out for infantry, making forces composed of lots of grunts without support weapons more viable, plus it streamlines the rules. Needs further testing but it looks promising... if you try it post your impressions!
yes, something that really makes a difference when you play with more characters, like many others... that's why I'm trying to get off my ass and finish more figures instead of playing etc. which in turn is why I'm not posting much here lately... but have faith, I'm on it!