Here's my assessment of how possible it is to use UT2k4's emitters to a similar appearance as Legend's system.
EMP 'nades: Can be done easily. Sprite emitter for flare, small colliding bouncing particles for sparks, maybe some trailing sparks for good measure.
Rocket Explosion: easy as well. Simple sprite, some sparks.
Bullet trails: Make them thinner and disappear faster, then it will be very close.
Jugg/Mortar/Mine explosions: Big mesh emitter for shockwave, lots of small sprites for smoke. Also simple.
Gas: Make the sprites bigger, and that will make it look thicker.
Smoke: See Gas
Shock Lance: Simply have the mesh/sprites used for projectiles have 2 side by side to make it appear double.
Rocket trails: Make them a little darker, maybe a few other things but nonetheless easily possible
Raptor boost flame: Make the emitters shoot faster and have lower lifetime, to actually look like a BOOST and not exhaust
XMP's bullet effects, for Raptor turret/Swingarm Turret/Winged Turret/Roundhouse Turret: Hmmm....this one's a poser. The best way to get the same effect would be to have many many large emitter sprites to look like before with wide spread. Also have the bullet traces come fast and not too accurately, and it should be possible.
Lowlands Giant Turret: Probably a beam emitter with a swirling laser texture. For the explosion, several static mesh emitters for shockwave spreading (sprites would look ghey for shockwave) and sparks that slow down with time (use velocity scale) and some explosions like the ONS Power Core explosions
If I missed something particular, tell me and I'll try to analyze it.
