By "change" meaning that i would correct, rectify or adjust previous prime fiction details or aspects then i think these 2 would be the top of the list:
- Tritanium does not react with "air", and all minerals mined are used to make alloys, to build up ships rather than being used directly (perhaps a better explanation as to how the manufacturing process take place)
- A slight adjustment in the way all factions regard "past" history and rediscovery their origins as former space civilizations. Details might have slipped in time in their homeworlds, but after soaring the stars humanity rediscovered their origin as being from outside this galaxy, and a general sense to discover where we came from (something that might spark a lot more people to EXPLORE).
Now if you are asking as to where i would like to direct the overall story arc of the whole game...well.....i would say:
1) Every "main" empire should have a "minor" ally, say Amarr and Khanid, Republic and Thukkers, with their minor allies being 0.0 entities who own a small number of constellations 2-3 somewhere just in the outer limits of the empire (best example would be federation + syndicate, but just spawning half the region the syndicate currently owns). This minor allies would be the main artifacts to creat plot, intrigue, betray and all that, facilitating players to relate with these rather than with the more established empire factions (enticing everyone to go for that 0.0 border)
2) Jove and SoCT would still be active in some way or another, enigmatic, all mighty, and not really aligned with anyone but still looking for clues (see first section). Their relation in CONCORD something of a contradiction yet still accepted.
3) Normal storylines would revolve around politics, diplomatic incidents, economic downturns, technological breakthrougs and cultural events. Each empire would have their own, and would cause ripples in their neighbors.
4) The "grand" unyfing story arc would be the discovery of revelations and prophecies sporadically that advance the riddle of humanity origins in this galaxy cluster (relics found, w-space, etc). And these would cause inflextion points in the storylines of point 3), stirring a lot of events happening.
But it would never happen, as CCP would need to tackle development and storyline as a single concept to drive the game. So no magic wands exists and will never be an option.