Satchel Charges are the opposite of defensive, they are used to breach enemy fortifications.
Maybe how much force you put onto the throw is determined by how long you hold the LMB, and the you take out the pin with RMB while holding LMB, so, simply pressing the LMB=weak roll, and holding down LMB=Stronger throw.
It could be kinda hard for the players that just started to play, but I don't think it would be super hard to get used to. Just some timing should be enough.