its not the panther clipper. (but I am hoping I am wrong! Cross fingers!)
The engine with landing gear attached to it swivelling is something present on the cheiftain/crusader/challanger.
Examining the pic shows a 2nd engine-plus-landing gear combo blurrily in the backround.
Super heavy ship designed by the Alliance department in Lakon, possibly alliance wanting to challange imperial/federal incursions with something big with SCO improvements so it can GET TO the fight and GET BACK faster than any fed/imp military ship.
From a strategic point of view having a fast responding military is critical when the galaxy is expanding due to newfound improvements in construction and colonization...
Regardless of ethos on invasions and/or defense... Better to be a warrior plowing a field than a farmer fighting a war.
Regardless of what, who, when or where... its definitely a BIG ship.