A house with a passage / underground to a cave or other house where certain loot can be found that is worthwhile.
Some more background story of the main missions in brochures that can be found at certain locations or hidden locations. Maybe an NPC quest to investigate that.
More background what happened to certain skell people or about Stone, Miler probably also about them in the second chapter Deep State.
The faction missions are too much of the same, kill sentinel commander, hack hacks and release prisoners.

Think of more challenges, computer hacking in heavily guarded fortress and failstop, on to the mainframe deep underground and in the meantime there is a lot of reinforcement from Sentinel and the Wolves. When escaping into the woods hunted by the Wolves and thus running hide in grass, mud to hit and run, exciting.