http://www.bungie.net/Stats/Reach/FileDetails.aspx?fid=22518428&player=Empyrus
This is the Firefight mode i made. Tweaked Firefight Classic, enemies and skulls are still the same except for the addition of Red Skull which increases enemy sight and hearing and lowers their damage reduction to 90%.
Two loadouts, Shotty/magnum and AR/DMR, both have 3 frags, no equipment, weapon drops enable but no ammo crates. No Radar, 110% damage resistance, melee and weapon damange, 90%shield recharge, no health recharge.
Give it a try, if possible with more people, tell me what you think.
It felt better than standard Reach FF offerings to me based on my quick test... but then i made it so i'm not objective about it.
EDIT the enemy's quite vicious on Heroic and they do seem to be more aggressive than normally.
EDIT i should add IWHBD skull... Well. For the next version then, after feedback.
I recommend using Buck or Johnson FF voice, those are the best.