Holograms for combat? I'm not going to bring in the Voyager books because of spoilers but from what we have seen actually on the show brings real merit to the idea for combat holograms
If you saw Renaissance man or Flesh and Blood you can get a real idea of what they could do.
How I would do it is not to make them as sophisticated as the doctor. Not to be left on all the time and not to learn how to sing
Just on for Emergencies and 2 subroutiens. Attack and Defend.
Imagine a ship that had holographic generators on each deck. Have these Holograms programmed in advanced tactics. They would have super human strength and speed.
Kinda makes boarding and taking over a ship harder.
Have a separate power source to power the generators incase of power failure and also have the emitters protected by small shield.
Thats just a defense idea! What about offence. Beaming a generator over to a Borg cube with its own scattering field and shield. All the sudden you could have 1000 holograms battling the Borg.
Not to mention a ground outpost defence against JemHdar invasion.
If you saw Renaissance man or Flesh and Blood you can get a real idea of what they could do.
How I would do it is not to make them as sophisticated as the doctor. Not to be left on all the time and not to learn how to sing

Imagine a ship that had holographic generators on each deck. Have these Holograms programmed in advanced tactics. They would have super human strength and speed.
Kinda makes boarding and taking over a ship harder.
Have a separate power source to power the generators incase of power failure and also have the emitters protected by small shield.
Thats just a defense idea! What about offence. Beaming a generator over to a Borg cube with its own scattering field and shield. All the sudden you could have 1000 holograms battling the Borg.
Not to mention a ground outpost defence against JemHdar invasion.