If the Imperial skin (C-Store skin that is now unlocked through fleet ship) works for the Mirror Universe Star Cruiser, then it stands to reason that the Regent skin will work as well. I will check on Tribble to see if I can purchase it through the exchange and if the skin unlock is available on tribble since I am sure I bought the Imperial skin.
Checked on tribble and didn't work since all previous C-Store purchase are not included. Bought Star Cruiser on exchange and I am able to use the Imperial skin. Therefore, unless there is a piece of code that states that the Regent skin doesn't work on the Mirror Universe Star Cruiser which is highly unlikely, then you can purchase the Regent and put the skin on the Mirror Universe Star Cruiser.
But can the Mirror Star Cruiser use the Wide Angle Torp?
Taken from the blog.
The Assault Cruiser Refit: Regent Class also comes with a prototype Wide Angle Quantum Torpedo Launcher. This torpedo launcher has been upgraded with a Wide Angle targeting system that allows the torpedo to lock onto targets that would normally be outside of standard firing arcs, providing a 180-degree targeting arc. This launcher can be equipped on any starship, but you may only equip one.