i would really wish that some day we get either some new engineering abilities for the ensign slot or new ones and some old may be lowered to ensign. Why? Because we have 2 to 3 engineer ensign abilities on cruisers while we have 2 ensign engineer powers (engi team and eptx) and if you are a tank cruiser u want to use 2 tac teams.. so ensign engi team falls under the table... and if u also got epts3 then the ensign slot gets pretty useless, because one slot (if u have 3) would be completly free and the two others would have for example eptw1.. and its a pain in the *** to keep 2x epts3 and 2x eptw running all the time.
As for excisting ones u could lower rotate shield polarity to ensign.. since no one uses the second and third rank of it right now. May also some other abilities.
And as a new ensign ability u could add a threat generating power or an crew revcovery ability.