For brainstorming purposes...
In order to add some spice, what about introducing, from time to time, some conditions to start, or to complete a mission ?
Eventually, some of them could be "optional" : a success will provide bonus points, whereas a failure will not generate any malus
Some examples :
1) "This mission needs to stay secret, and so will need experienced team : equip your craft with maximum six units of minimum rank 'sergeant'"
=> Also if craft does not fulfill requirements, it will not ne possible to land
2) "This mission has to be fulfilled in urgency : complete it in less than 15 turns"
=> Skyranger go back home at end of 15th turn, also if mission not completed before, this will be a failure and all soldiers not on board will be lost
3) "You will not be able to use lethal weapons for this mission"
=> If craft contains any lethal weapons (based on battletype ?), it will not be possible to land
4) "This mission only requires rookies equipped with one handed weapons and no armor"
5) Rescue Mission (cf. Unknown Hero)
6) Large shipment of new type of Alien weapons
"Our Intelligence service has reported the delivery of a large shipment of a new type of Alien weapons.
We absolutly need these prototypes to know exactly what the Aliens prepare.
We know that the delivery will take place in the following week (from June 12 to 19) somewhere in Asia, but we don't know exactly where.
We have 5 hours to attack the UFO after landing.
Monitor your radars, and try to not shoot the UFO in flight, wait until landing.
Exceptionally, crew will consist of Mutons and Ethereals with Sectopods.
The report precise they are heavily armed, expect lot of Blaster Launchers."
*
Mission Bonus-Malus:
UFO ignored: -2000 points.
UFO destroyed: 100 points.
Landed UFO assaulted: 300 points.
Weapons recovered: 100 points, 100 weapons --> sell them, use them.
New Alien Technology to research.
UFO crashed and assaulted: 150 points.
Weapons recovered: 100 points, 100 weapons (random, 10% chance to recover weapons, random weapon number).
New Alien Technology to research (only if at least 1 weapon recovered).
7) If player has not captured and interrogated any aliens at all, then encourage him to do so.
8 ) If player only captured and interrogated a soldier type, then encourage him to try and ID+capture medics/etc.
9) If laser weapons were recently developed, encourage trying him out by saying R&D is eager to see how the weapons perform in actual combat situations.
10) True missions with some goal(s) to be reached (like extract VIP civilian, assassinate Alien Commander, ...) that would end the mission, like shooting the alien brain in the cydonia mission.
11) "Hold the line" mission : have to resist X turns against a huge alien attack
12) "This mission ..."