There are various sub-quests available in each of the Story Missions and Order Missions throughout Armored Core V. While some are cake walks and don’t require much effort at all to accomplish, there are those that are painfully difficult and will require you to adapt your AC to the situation at hand. The Order Mission sub-quests usually have only 1 or 2 requirements to meet such as taking a maximum amount of damage and/or finishing within a set time limit, but can also include things such as taking down a boss AC lighting quick.
The Story Missions however, have a long list of requirements that must be met, making things a little trickier. If some of the sub-quests are proving to be a little too difficult for you to nail, don’t be afraid to call in some reinforcements with mercenaries! They can make all the difference!