Esp. Important now that it looks like new edrumin4 units are more than a year away
![Sad :-(](./images/smilies/icon_e_sad.gif)
I'm not sure how complex such a circuit would need to be, my initial thought would be the switch would just have to trigger the momentary release of a piezo-level current and voltage. (This would be for crossstick and rimshots so lack of velocity info wouldn't be too annoying, or maybe could be detected by the main piezo). Hmm actually maybe it's more a routing issue, eg if switch a is triggered send piezo output to output a, if b is triggered send to output b, if neither is triggered send to output c, if both then output d.
There is a circuit schematic that does kinda the opposite of this up at https://edrums.github.io/en/diy/keith_pp_2_ps/
Schematic of what I believe the two switches are like on my device / how they share a single output conductor at viewtopic.php?f=33&t=1584&p=11256#p11256