Time to summarize the changes we can expect from the 2.1 update based on dev updates and newsletters so far:

General changes:

Persistent, mostly generated NPCs will be added: mission givers + engineers, will have some form of mug shots based on the future commander creator/character editor
Relationship with minor faction will determine which character will be mission giver
NPCs will give feedback about the situation of a minor faction and ways to support them
Engineers have their own backstory and specialization
Engineers are spread throughout human space (initially ~30 engineers)
Engineers can modify weapons and modules (using loot)
Player ranks/alignments/other parameters affect options offered to them by engineers
There is a minimum requirement for player ranks/alignment/stats for using an engineer's service
Engineers are found on isolated surface facilities
Wrecks will be added (unclear if surface only or space as well), loot and crafting gameplay will be associated with wrecks, concept art of SRV scanning data recorder in wreck was shown
Options screen will have collapsible sections for easier navigation
Adding new hardpoints including huge weapons (concept for large+huge multicannon shown)
Asteroid graphical fidelity improvements
Star light has been fixed so that it retains its colour over distance
Bookmarks will be added
Systems/planets/stations/asteroids can be bookmarked
Bookmarks have a custom text, can be edited and deleted
Bookmarks will be visible on the galaxy map and can be selected as navigation target in route planner
SRVs will leave tire tracks on planet surfaces <NL #116>
Community goals will be marked on the galaxy map and system map, will also appear on any bulleting board regardless of system <NL #116>
Community goals may have multiple commodities involved. <NL #116>
"Revamp" of outfitting screen, different classes have different purposes, will become more clear <exploration livestream>, <synopsis>


AI changes/fixes:
Flatter difficulty curve for low rank NPCs, more challenging high rank opponents
effective missile + torpedo usage at high ranks (when opponent shields are down)
Increased damage avoidance by high rank AIs
High rank AIs flee for recharging shields before attacking again
High rank AIs will try to counter players who use the reverse thrust tactic
AI can't use energy weapons when overheating anymore
chaff spam decreased, only using chaff when taking damage from turrets/gimbals
AI doesn't get stuck rotationg in one place anymore
No more hatch breaker spam
Better pip management for fleeing and pursuing



Changes for/to missions grouped by broad high level concepts (dev updates from January to March):

Personalisation
persistent mission givers, treatment of player depends on player ranks/reputation/alignment
Docking greeting messages change depending on alignment/rank
NPCs remember having had contact with the player before
NPCs inform player about the status of a faction (civil war etc.)
NPCs inform player about the effects their actions are having (status changes for minor factions)
Mission selection improved depending on a factions status

Progression
One additional positive alignment level will be added to faction alignment (Hated, Disliked, Neutral, Liked, Allied, +?)
The mission board in station services replaces the old bulletin board
Expanding the functionality of the inbox so that messages will persist

Variety
More missions are available at the neutral reputation stage
Rank requirement for missions are removed - the rank will now be an indication of difficulty + rewards
Missions will be generated around players's Pilots Federation rank
Three stage hierarchy governs mission generation:
Minor faction state
Market type at the port (e.g. mining missions in extraction economies)
Government type of minor faction (e.g. dictatorships => overt assassinations)

Missions will provide description why they have been offered and what effect their completion will have
"Barrier of inconvenience" for some of the mission elements reviewed e.g. "not having to drop out of supercruise to listen to alternate offers"
"The time limits for missions as well as which elements make them easier, or more difficult are being reviewed and addressed."
The cockpits will receive a clock
USSs for missions will now generally be located at specific bodies within a system, not randomly spawned as time goes by
Bodies with USS signals can be detected with the discovery scanner, normal range limits apply
Nav beacons can be scanned (in normal flight) to receive system exploration data and to reveal mission locations
USS placement depends on specific places like "traffic lanes" and "hubs" in a system
USS can be scanned from supercruise to reveal more information about them!

Consequences
Exact indication of influence isn’t (!) part of the mission changes (only indicates positive/negative impact) as of 2.1, unlike reputation and state changes, which are indicated
"With minor faction states we’re intending making their effects more noticeable on available missions, ship traffic and composition, and markets." (Less subtle changes)
"authority response if they are attacked will be sharper."

Rewards
"treasure" locations as new additional mission reward type (missions may lead to cache with vouchers/other items => crafting! )
Crafting materials as additional mission reward type as well as hard to obtain commodities and "salvage only items". Some commodities possibly only obtainable through missions.
"varying rewards for effects on minor factions which are getting a balance pass to make changes in state more likely as well as more noticeable"
"rewards will be balanced to scale better with difficulty and also be more lucrative if you’re well regarded by the minor faction"
"conducting a pass through the mission templates to make them more reliable and address issues seen in the current build"
"adding more scenarios for the various mission types and also to better reflect the active states in the system"


Release
Beta release aiming for May <NL #114>


Sources: dev updates and newsletters from January to now. Any more things I've overlooked?