Out of the 5 FX loops I have integrated in my rig, two are Reaktor based. I had previously set these up with fixed multiFX processors. I have yet to get into selecting snapshots via MIDI and I am not quite sure how that is done. Selecting though parameter change may very well be the only way. Because Reaktor has numerous FX to choose from and they all seem to use snapshots, I wonder if snapshots from a variety of FX can be placed in a folder and treated more or less like a bank, so that when a snapshot is called, it loads said FX instance. Maybe that is a stretch and something best left for a Reaktor forum, , but you seem knowledgable in this topic.
In any case, I also placed Guitar Rig and Reflektor XT in two of the other loops as well as an Arturia replication of the classic Mutron Bi-Phase as that was an instrument I had years ago that I was fond of. Using Kushman Elements I began building a BiPhase preset list and was preparing to experiments to see if I could select those via VEP parameters while the plugin was inserted in an audio bus. Guitar Rig loaded within Elements fine and I have discovered it is a versatile multi FX processor that needn't just be used for guitar FX. So I am not just using Reaktor FX is my main point here.