Technically, photon torpedoes would be able to fire any direction with a minimum arming distance - they're guided weapons, afterall. You may fire them out of the front of the ship, but they should be able to maneuver around to hit a target behind you if need be.
That wouldnt work with plasmas, though, which have no onboard guidance systems (considering they're just a ball of energy).
The Somraw, K'tinga, D'Kyr, D7, Kumari, Xindi carrier, Xindi escort, and the T'Varo are all older than the Constitution Refit and yet they are tier 5. The Constellation is made up primarily of Connie refit parts and it is tier 5, there is no logical reason whatsoever for the no tier 5/6 connie rule.
It would 8e interesting to have a manual lock on system, that you had to activ8te. It could launch a torp, or 8urst of torps at any target in range, 8ut you would have to line up the shot, making it useful as a first strike maneuver