Thought I covered this...
Along time I did a section on 'Holotech' including ESH's (Emergency Security Holograms). The best about these were: the 'living' shield ability (phasers don't really effect 'holo's), the surprise (if fourteen 'jaundices' show up outta thin air, bad guys goin' down...even if they're a Gorn:))
'nother thing though: why limit to 'single' function? Voy's EMH could have merged it's ECH programming/protocols/perimeters with the existing ones; anytime a conflict came out, the EH system could/would have weighed the situation, then decided based decision on/from 'the best side' (EMH, ECH, or both).
Just a few thoughts, I'm off to design an EMMH (Emergency Marine Medical Hologram...in the words of Bill Cosby, "This is called 'fun'.":D)