You definitely need some envelopes. Consider at least a dual ADSR, or a module with multiple AD envelopes.
The Pluck is a bit redundant, as there is really nothing it can do that the Rings doesn't already do (unless you had in mind using two Karplus Strong type voices simultaneously but that would require more complex sequencing).
The Elements is capable of a wide palette of sounds not possible with standard VCO / VCF / VCA flow, but the resonator portion of it is already there in the Rings module. Unless you really want / need the odd sounds Elements can make...... you might find yourself just using the Rings for the resonator when not using it as a voice on its own.
I'm sure more experienced people might have additional thoughts but those were the obvious observations to me.