Let me just point out a few things that may be accomplished with it:- Introduce new players how to play the game, mostly by progressively introducing technologies.
- Deliver interesting background stories to all the races that take part in the campaign, with their fates perhaps even set interactively changing in respect of how maps ultimately play out.
- Perhaps being able to shape your chosen race by the evolution it undergoes as it adapts to the campaign. This could be even implemented in a retroactive style, like "Pre-Industrialized Start" where you basically build up the strength & traits of your starting race on their native world until they have enough requisites to become a spacefaring civilization. (that sounds now like a minigame in itself, but it could be easy implemented by generating the map not in space but with a planetary outlay with the nodes being just islands in a sea)
But once you leash out in space you start at a relatively tiny map, with a severely restricted technology tree, so new players won't get lost into stuff that's basically irrelevant/overkill for that map.
Every map could come off with unique victory conditions in itself - for example, colonize/inhabitate a specific planet/system; defeat/ally specific races/empires, research a specific tech, construct a specific building, you name it
Once victory is achieved the player is taken to the bigger galactic overview to select the target of his next expansion. The choice would be kinda limited in the beginning but this will change as the empire subseqently gains in terrain & technology.
Every map will permit you to find new technologies which are then added to the techtree & these findings can be used from that point onwards. This means, that there are maps which may not be conquerably (or only very hard to) if you lack some specific techs. And because a player is free to choose his path [more or less, a good campaign wouldn't implement such trappings early on but as a method to increase difficulty later on] this kind of randomizes to a decree how the global universe will or can be ultimately played out.
Ofc you cannot jump at a new galaxy with your current strength - the sheer distances may only allow a few basic requirements in order to build a base on a suitable planet. As the game successfully continues this ability could increase to lead to Accelerated Starts, so a player doesn't have to play through the same start but also swiftly learn how to use midgame & endgame techs. Ofc the opponent empires gain these starts as well as do natives become increasingly resistant.
I've yet no clue how such a scenario could be finally be played out. The military battle of a complete colonized galaxy versus another would surely be dull & system-wrecking. Perhaps there could be a quest that is inherent to the story, like the universe is dying, you need to find (and fight your way through) the wormhole to the next universe to ensure the survival of your race - legend has it it lies somewhere in the distant Orion sector but mysteriously noone ever reported back from there^^
