Hi All
Are you sure the vibrato cant be transferred to after touch, as all Wersi instruments built since 1984 (The first digital versions) have the vibrato built into the voice, but when you activate after touch it automatically gets transferred to player control.
I would check on this, as I find it most unusual that manufactures would not allow the vibrato to be transferred. (Also check in settings as there may be various options available for after touch control)
Enjoy whatever instrument you play

Bill