I also used the "RECALL M/E CONFIG" scenario when I introduced MP-II at our facility.  Basically, it allows you to configure MP-II once, and then recall it on a snapshot by snapshot basis.  That said, a number of snapshots that I used would put the individual MEs into MP-II mode, but other snaps that were created before MP-II was enabled would still work, essentially switching MP-II to a dormant state. One word of warning:  if you run things this way and end-up delegating a DME channel to an MP-II partition, the DME will still be acquired on the 'sub' partition (like if you had a DME wipe selected non the sub portion of the ME).  You'll just need to manually release the DME channel, or clear it from use on the sub-side before switching away from MP-II.

I don't know what ver of 7 had this feature...so you may not have it....but if you look at menu 7331 you may see an option named "RECALL M/E Config"..on the right side. Having this option on, allows snaps and effects to recall the M/E Config.  So for instance, if you want M/E 1 to be in MP2 for one effect...but not the rest, your one effect could put this M/E into MP2. ( or MP or back to Standard)
If you don't have this option, then it would follow the setup file...so you would either need to reload to get it to normal up, or just go into menu 7331 and reset it manually or  better yet, use a menu macro to go back to standard mode and another menu macro to get you back in  to MP2( as well as change any other settings for MP2).
IMO for where I work,  it works great from a flexibility perspective. I run in the "RECALL M/E Config" on. 
One thing to remember...the actual state of the option to Recall M/E Config is a setup function...so you have to resave your setup(s) with this option on.  If you choose to go this way, I would also check all effect/snaps to make sure nothing wacky happened.  I built from scratch w/ this option on, but I am not sure what wackiness may happen if you turn it on for an existing build..I woud assume nothing...but I would keep an eye out.
 Curt