Laws of Reality

You can wield a lance with one hand on a mount. With the the Dual Wielder feat, you can hold two one-handed weapons at the same time. As a small race, halflings can’t easily use any weapon with the “Heavy” property, which the Lance does not have. It would be entirely legal by the rules for a 1 meter tall halfling fighter on a riding dog or pony, to attack with two human-sized Medium lances, while also having a mount that easily fits into most dungeons. Or even a beast master ranger, adding some surprising damage along with extra survivability to your mount.