What you are saying then Hebe, is that the database of the game tracks the Group fine, but cannot "spawn" the Group since the Leader cannot spawn, correct??... the "easy" fix then is to change the Leader unit, and make the Isle trawlers a percentage call for later in the game's timeframe.
So riddle me this then Hebe, if a ship is NOT the leader, will it cause trouble when the group attempts to spawn, if prior to the ship's "existence"? SH4 does not do this. It just spawns the ship... it might be "naked" without a skin, but it spawns...