Some points about double-handed flails

I can see this mangual used beside light infantry support who, once the halberd is disabled, rush in and dispatch the halberdier, thus clearing the way to advance. The kicker would be clearing the entanglement to engage the next opponent; take too long and you are effectively out of the fight. Alternatively, having multiple manguals; once the halberd is entangled and the soldier dispatched, a fresh weapon is provided as they advance, worrying about freeing the weapon after the fight is over. I can also see the mangual being used against a halberdier formation, potentially entangling more than one. Even if the halberdier has a dagger, they would be at a disadvantage against light infantry armed with swords. The scenario is neither a battle nor a duel, but fighting guards protecting a nobleman's quarters in hallways and small chambers within a manor or castle. Of course, this is all speculation. I think the reason manguals never proliferated was due to the growing popularity of muskets, which was growing in use around the same time. A musketeer makes a halberdier anachronistic.