RE: "tactical"
I agree with Maine, a "tactical" rifle should be a plain and simple, down and dirty tough rifle. If it were me I'd go with a basic M4 style carbine with an A3 upper. On the upper I'd mount a RRA EOtech sight base that has both the EOTech holosight and the A2 iron sight. I can see the purpose of a holographic sight on such a rifle because it allows rapid but accurate aiming in all light conditions with both eyes open, but with that sight base system one also has the iron peep sights to fall back on when (not if) the EOTech fails. The only other thing I can see being a practical accessory is a good high intensity weapon light. One can never understate the importance of positively identifying ones target. If you shoot an innocent you'll do time, guaranteed.
I wouldn't even go with a free-floated handguard. It's a nice accuracy feature, but "tactical" usually means short range where tiny groups aren't that important, but a tough reliable rifle that can double as a melee weapon in the event of hand-to-hand combat is.
Mike