The current version does have a feature similar to Q3 CPMA.. if you switch guns the time till you can fire again is lowered to 1 second (or just kept the same if its already lower). So if you fired a gun with more then 1 second refire time (actually the nexgun with 1.5 seconds is the only one) you could switch to some other gun (mortar for example) and fire again sooner then someone that did not.
The idea was to make it rewarding to switch guns and also to choose, not switching but concentrate more on aiming or to switch which takes some concentration away. However i found it easy to get used to this and i think i'm able to do it without throwing off concentration or aim. Also because of the short weapon switch times in Nexuiz one is able to switch forth and BACK to the nexgun and be able to fire at 1 second intervals instead of 1.5. So so put it to the extreme: In 15 seconds there is a difference between shooting 10 or 15 times resulting in 1400 or 2100 possible damage with the nexgun..