Marketing solves your problem. How's about this:

"At [your company] we have listened to the input of the military and law enforcement community in order to make our entry tool as versatile as possible. For this reason we have intentionally left the back of our [combination battering ram/halligan tool thing] unenclosed so it also may serve duty as a munitions carrier in an emergency. The open top also serves as an transport device for removal and safe containment of hot smoke/tear gas grenade containers after training exercises.

The open backed feature which is unique to our tool also allows the end user the option of easily adding lead or concrete fill at a later date should your unit require a heavier ram for use in areas with exceptionally heavily reinforced entry points. The mass of our tool is sufficient for the majority of professionals we have consulted, but at [your company] we understand that unique operating environments sometimes require unique tools. Our open backed ram allows the end user to tailor the weight of the tool to his or her exact requirements. For recommendations and instructions on how to add weight to your ram, please see [print a manual or something]

We at [Your company] understand you may not want the flexibility and versatility an open backed ram allows. For this reason we offer "fully welded and enclosed" option at a nominal fee. Simply check this option on your order form and we will add a .125" A36 steel plate to the back of your ram for an additional [$20 sound right?].