First you need to set the dismemberment allowed on the server using the g_dismemberment cvar (It's something like that, g_dismember, maybe, just use cvarlist to check it)
Then each client (including you if it's a listen server) needs to turn on cg_dismember (again, I think that's it, it may be cg_dismemberment, use the cvarlist command to double check me)
And with the cvarlist, you can use filters.. so:
will get you all cvars starting with 'g_dis'
I'm just too lazy to boot up JKII myself