i think the only 2 options u have when your sub is destroyed: to pay with gold (real money) or to abandon the sub permanently - it;s total bullshit

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loosing a sub, u played for a long time and payed with prestige (an event that will be quite frequent) forever, it's devastating. we should be able to recover it with prestige - payable in an unlimited amount of time after. so we can play with other subs (or the auxiliary one) for a time to be able to get the prestige to redeem our leveled up sub.
getting the auxiliary typeIIA as a replacement and having to start from scratch, makes me abandon the game really fast.