Actually I think you might be able to do it with events, but it would be VERY VERY limited in way of AI, and a script would be not only better, but much easier than trying to do it though events. Tsuno knows a lot about RPG maker, so I trust him when he says that you would need a script, events would just be very long, complex, may cause lag, and may not even work.
The bad news is that I'm not so much of a scripter, else I would attempt a script for this, but if you do try to do this with an event, you may be able to get away with clever use of Status effects, common events, and battle commands.
Now I'll warn you that this is probably going to be more bother than it's worth considering the shear amount of complicated conditional branches, variables, and other factors to factor in. In short I would either advise you to find a script if possible, or just work around it and do the best you can without it, if you do *NEED* it, then try playing around for a bit with the above items, maybe you can find a 'solution' for yourself, but again I would advise against it.
Maybe if I find some free time or I feel the need for a challenge I may take this up, but for now I'm sticking to thinking that it's not worth it.