a plethora of additional ideas:

Another 'player created' asset item type to add:

13) Quests - can be as simple as a new fabrication/repair formula for a piece of useful machinery (U-Make-It) or repair/maintenence mission for some new Terrain situational assembly/installation (lots of maintenance Quests in leaky Rapture). (( EXAMPLE - a leaking window with nice spurting effects and a large puddle, that requires welding repair)) Many Quests follow formulas with simple fill in the blanks (destinations/NPCs involved/NPC dialogs/hints/fetch items/etc) and most of the life of them is the Quest text with story/miniplot/interesting descriptions/motives
7b) A behavior AI scripting system for the players own controlled 'Team' NPCs (scripts shareable to other players - applicable to game run NPCs also). They are not 'cheats', but 'instructions' that would keep the players ex-Splicer/BigDaddies and other agents working while the Player is offline (and moving about the city on tasks that would make the city actually LOOK like a city with people in it doing things instead of the talking mannekin NPCs alot of MMORPGs are limited to). Player use -- applying these NPC 'AI' scripts is more like setting parameters (really are plug-ins then with config settings) and picking missions/tasks -- not really 'programming' (they implement flexible if-then logic for decisions, as well as pre-canned condition tests built into the 'Team' mission/task templates.

If I didnt mention it before, the Player review/vetting of all these new Assets is only the first phase -- as the company would then do its own vetting/validation before actually adding them to a running game world.
- Most of these things are built on/recombined from sandboxed 'sub-routine' Templates the company would supply,
- They would NOT allow Cheating or Griefing - only access to the same info and actions a player would have.
- Any 'problem' script content would first be found by the player inspectors/testers who are rewarded for finding errors/disfunctions (in game rewards, not monetarily).
- People who submit intentionally problematic items are afterwards restricted and not allowed to progress onto more complicated/challenging assets.
- a Creator Ramp (leveling) progresses to larger assemblies (complex scenes) made of many small assets -- props/terrain/NPCs/thematic decorations interlinked by scripts/quests/placement rules.

Another aspect for the development effort required to implement the 'player created asset' MMORPG game model ----- the server/client mechanisms and tools can be REUSED for creating other similar MMORPG games (something like half the work would be reapplyable to a second/third/etc game of a similar type
.... example - a X-COM MMORPG game .
Again, an important factor is the production savings ($$$) by using the player created game Assets/content (which IS one of the MAJOR expenses in these MMORPG games), and making possible MMORPG games in niche genres that companies wont touch right now as financially unviable.
SO much the better if the company already has a seed set of Assets from an existing solo game to start the core/prebuilt areas of the map (like Bioshock with 2 games and a bunch of DLC materials).

Normal People again ... :
Rembering the selection of player Avatars from the BS2 MP game -- they look normal -- were from before the heavy splicing became common in Rapture. With the MMORPG's 'Cure' for the negative aspects of the Adam addiction, we would have NPCs once again no longer looking like malignant mutants.
The 'Cure' of anti-Adam might be again right there in the Sea-Slugs, who dont turn cancerous/behaviorally irregular even though they are full of ADAM. Tenenbaum's solution would mean restoring people back to a more normal state or at least supressing the negative ones - we still want plasmids for the FPS part of this game, though many of the technical ones have greater use in the repair/rebuild/restore overplot.
Part of the game I would like to see is having the ability to crawl up the walls (maybe not the Player??) Think of how useful to repairs that would be, or to counter 'wild' Splicers in the unreclaimed parts of the City. That would be that 'Cures' wouldnt have to destroy plasmid abilities and there might actually be a reason to safely (via anti-Adam) 'enhance' players/NPCs with NEW abilities/skills/pysicals/intelectuals as was the original vision for the ADAM. On the other hand, players might only have normal abilities but more tools to use.

Cityscape :
The external part of the City can be part of the MMORPG. Work ouitside to patch parts of the City and make them water proof again. Gather raw materials to make certain things (Ryan planned to have Rapture 'self sufficient', so there is a lot of industrial stuff laying about somewhere in Rapture, as well as basics like 'Fishing'. There would be areas quite a distance from Rapture city center - mining or oil drilling and outlying industrial/manufacturing or greenhouses in tunnel complexes that are all candidates for player interactions. The Player could use a Big Daddy Suit Skill for external work and/or Submarines and or Bathispheres. The terrain outside need not be that complicated to create, with existing tools like Bryce capable of creating appropriate landscapes for huge areas of the outside ocean floor.
There are wrecked parts of the City which probably never will be restored, but become hunting grounds for salvageable/useable parts and resources (like for large sections of the special Ryanium 'glass' to replace sections blown up by certain people previously, or cracked by sinking airplanes.)

Inner Terrain :
Besides the outside Ocean (and all the fun sealife to fight), there are parts of Rapture we really didnt see that much of --- utility ways to access all kinds of machinery and utility lines :
1) Sewers and their extended facilities, including lots of sumps
2) Fresh water pipes
2) Electric power lines
3) Air circulation conduits/ducting
4) Heating systems from the geothermal core (hot water)
5) Telephone/ Cable TV/ Pneumo Mail
6) Cooling water for machinery (seawater)
7) Transport tunnels to move garbage/goods/maintenance personel
8 ) Fire supression systems
9) Security systems
All these things in many places have been broken, damaged, disconnected, are submerged, sabatoged/vandalized. The Player would want to restore them bit by bit in his claimed 'project' part of the city, joining up with the restoration efforts of others Key junctions/connections cooperatively restored to bring the City back into existance.
Major transport systems like the Trolleys and Atlantic Express would be large team efforts (a source of many many sub Quests to rebuilt these large systems section by section)

Vertical transports like elevators and stairwells would also be things to get working again (and give access to new places and adventures).