[Ides]

In which case, give it two kinds of shells, one which uses the Baneblade template with higher strength and one which uses orbital bombardment.

Hmmm...

Range: 36'-72' Becomes barrage without line of sight.
Speed: lumbering. May not move and fire ordnance, may not fire next shooting phase as troopers reloading (may fire turn after that) May move while reloading. The *insert name here* cannon has a limited supply of ammunition for the *orbital bombardment template rounds*, every time a shot is fired roll a d6, on a roll of 1 the gun has depleted its stock of these shells and must revert to the other type.

Special Rule: Zeroing in. At the start of the game, before deployment. Choose (1 or 2?) terrain pieces, buildings or landmarks. Any shots aimed within 12' of these do not scatter. Between 12' and 18' scatter D3 inches instead of D6