Ok, so I need help with my idea.

This happens in game.
In Map Pack 3, you have some stuff like wine bottles, tables, plant pots, and crates. If you step on wine bottles they would break or fall over. If you have Forum Wide Banana Machines (The computer that allows you to torture enemies) and you set it to physical drag, and attempting to drag any of the listed objects they would physically react, and I remember smashing some toilets against a Coalition Clone and thinking "How can I get this to be in a grenade? Pulling out a toilet when someone shoots off your gun and throwing it at them would be cool."

So, how can I make those objects into a "bomb" or a grenade?

This would actually make a great minor mod. I'd gladly convert all the MOSRotatings in MP3 to TDExplosives if you want.