Fearing the "second system effect" in my rewrite of ESMS

I'm still in the early stages of rewriting ESMS, and I begin fearing that it suffers from the "second system syndrome", which is described by Wikipedia as:

the tendency to design the successor to a relatively small, elegant, and successful system as an elephantine, feature-laden monstrosity

I keep thinking of new features, and before I even have the time to design how they integrate into the big picture I think of more new features, and my users drop in a few from time to time. I've also mentioned the problem with my users' lust for features before. I think I have to slow down and create a clear image for myself of where ESMS is headed. I guess I won't have much time to plan it before the trip, but when we get back in March, I hope to have a clean, rested head, and finalize a design for the new version.