In case your number one aircraft is a mudmover, the other planes going to have the same available weapons as that.
With an example, if you start with an A-7 then your F-15 will only have Sidewinders for A2A duties. It is like that from the begining of the game series as I can recall.
Number 4 is most of the time pain in the butt, also depends on how close to the target you asign a target for flight2. Other than that, if they got the weaps, they always going to defend themself from SAM and AAA fire, thus sometimes ending toasted.
An other note as I found in mudmoving, if the asigned targets are eliminated 3 and 4 will auto target the closes AD unit then continue with the rest untill they winchester.
edit:GrViper was faster ;o)