FREE THE HEAVY SLOT!!! Allow us to dismantle or store the quest gun in vault to free up the slot. We can buy a new & higher level one from Benedict in the tower. I have a low level Legend of Acrius shotgun locked in Heavy weapon slot that I will never complete because it is impossible to assemble a willing raid team to complete the quest.
You can get Seals from completing the Castellum, you don't even have to finish any of Calus' games.