Just asking if the LMMS instruments will have a assignable mod wheel built in to them? If not I'll start a mockup.
mockup based on the lfo env tab

how to:
1 To assign right click any knob, button or slider.
2 Click assign to mod wheel.
3 Then go to the mod wheel tab to set the mod slot. To enable or disable a slot press the mod slot button next the name of the mod slot.
4 To assign the Velocity to the right click in a empty space in the mod wheel tab then click Velocity.

how to remove:
To remove the Velocity or any other one to the right click in a empty space on the Velocity mod wheel LFO tab then click remove mod slot.
The mod wheel tab can have unlimited mod slots.

The rage box is a master range box that uses the sitting you have set up in all mod slots.

Update For those LMMS plugins who have a built in modwheel like ZynAddSubFX or vsti right click in a empty space then click modwheel.
To remove the Velocity or any other one to the right click in a empty space on the modwheel mod wheel LFO tab then click remove mod slot.