ok, so you want to record more than 2 tracks (ie 2 stereo pairs) like the source from say schoeps > v3 and mbho > minime at the same time...
yes absolutely this is possible, but you have to have it set up right. first you need mutitrack software. i would not recommend having 2 separate audio applications open simultaneously, that sounds like a good way to crash your laptop. let me give you a simpler example....
a friend of mine has the nuendo multiset (an 8-in box) which has a pcmcia interface to his laptop (picturebook). he runs sonar 2.0 which allows multitracking, thus he can use more than 2 inputs, like 4, and record off of 2 rigs, a rig and the soundboard (stereo), etc.
in theory all you need is enough inputs and software than can handle them all at the same time. in theory if you have a mme and a vx pocket and can set cool edit or sonar or whatever software to use both of them, you'd have 4 inputs and could use them for whatever sources.
using one piece of software may help synchronize the files also.
hope that makes sense and helps.