One of my many ideas for a mod is a new structure called a siege platform.  It would essentially be a hybrid between a siege frigate and an antistructure cruiser, but as large (and as tough) as a starbase.  It would be constructed using constructor frigates (or the Jarun Migrator) and would have very heavy armor.  The TEC siege platform would be the toughest and have the most damage (~150-200 DPS) and would have a HUGE range, but would be expensive, slow, would do ther least bombing damage, and wouldn't have any abilities, aside from one that would allow it to convert back to a Raloz heavy constructor for a nominal fee.  The Advent one would be in the middle- its speed, cost, firepower, range, and durability would be between the Vasari and TEC one.  It would be unique in that it could carry up to 4 squadrons of bombers.  It would also have five abilities- including one passive ability that would simultaneously allow it to convert energy attacks into antimatter, build replacement strikecraft instntly and have extra strike craft in its squadrons.  To keep it from being OP the strike craft would cost antimatter (about half as much as normal) which is VERY important, as it only has ~200 antimatter.  Like the TEC one, it could convert back into a contructor for a small fee.  The Vasari one would have the least firepower and damage, but would be very fast; in essence, it would be as tough, fast and powerful as a midlevel cap. ship.  It would be very cheap to build, but could not convert back to a Migrator- it's a disposable siege weapon.  It would have a few passive abilities, but nothing special.  I hope to create these structures soon.