In the Acoustic Agent expansions or the full version of Groove Agent 5, the kits have at least one alternate Snare and Kick to choose from, recorded in the same room as the rest of the kit.
Also in the full version, you can load up to 4 different kits in separate slots. By using the Hardware Controller Mapping function, changing all kits to use the same MIDI channel, then soloing the cymbals that you want to use, you can add/remove/replace cymbals from your drum kit.
Just keep in mind that the cymbals will be routed to different internal Groove Agent buses if you do this. You can get around that by routing your cymbals to a Group Track in Cubase.