>>95948110
Youu ccann fit them in if you want to. As mmentoined, SSDs are very rare, they're really moree of a show-of-force symbol and reward for the most loyal Moffs/Grand Admirals.
There are a number of classes larger than the ISD that essentially fit in that category. Too big to deploy economically, but they serve as station flagships in the hundreds of 2nd tier sectors where you don't want to deploy a super-rare Executor, but it just looks better if you give the sector command something bigger than 'just another ISD'