There is no way IMHO they would make Roimulans loyal to the Tal Shiar playable.
Start thinking through things:
Any playable Romulans will get the same Feature Episodes as Feds and KDF. They will also be teamed with Feds and Klingons in STFs. There's no way Cryptic would make that exception.
Seeing as how the Tal Shiar and the old Empire loyalists want the death of all life in the galaxy (heck, including Romulans), that teaming dynamic wouldn't work.
The New Romulus Romulans will be the only ones that will be playable.
The old Star Empire doesn't serve the Iconians like the Tal Shiar. They're having civil wars right now, but they're still the proud Imperials we know from TNG. And I'm sure they'd team up with the Feds and the KDF again if they had to fight the Iconians.