N7 is basically the Alliance's answer on STG & Asari Commandos. That's an Elite Special Unit designed to do the job if everyone else failed.
Not to get too O/T, but that isn't really what a special operations unit is for. While there is occasionally some mission overlap between conventional military units and special operations units, generally they are different tools for different tasks.
Say you had a town sitting on a strategic crossroads that needed to be seized, but was occupied by a battalion of enemy soldiers. That mission would go to conventional military forces (infantry, likely backed by armor, artillery & air support) rather than special operations, though it is possible that special operations could be utilized in
support of the conventional military forces carrying out the assault.
Typical missions for Special Operations units would be long range recon, hostage rescue, counter terrorism, unconventional warfare (such as aiding resistance groups against a common enemy), direct action (examples include the killing of Bin Laden, and the Norwegian raid on the German heavy water plant at Telemark in WW2), search & rescue for downed pilots, ect.
Anyway, Ashley looks hot in the recent trailer. And I love the new armor.