About mortar :
fence in front of mortar position block mortar unit and cannot fire (try with GFX's mortar) so to build sandbags into the model and avoird the problem is a great idea !
And how many man it? from the screen its one. 2 would be more realistic.
Maybe, but IMHO only one is better, because assigning static position commander -like GFX done- is unrealistic specially when ennemy are close
Anyway you could yourself join mortar to a group, isn't it? (from Editor keyboard F2)
About size of the pack : When you like you don't count, 40Mo 50Mo even 80Mo, doesn't really matter, and this file could be hosted by file sharing soft users (Kazaa,etc...)