I've toyed with something similar:
Auto-destruct
SV bonus: +3
Range: 3" radius around model
Pluck modifier: -1
Cost: 10
Notes: One use only, model is destroyed after use.
This essentially works as a slightly larger, more random explosive grenade centred on the auto-destructing model, rather than thrown. Even so, it can affect models not in base contact, so is treated exactly as a shooting attack in all respects.