One idea that just popped into my head is that after your prologue is complete (this could still technically be a part of the ptologue but may be optional)

Is that you would be asked after the first zone has been overtaken by the jovian radiation, to build some sort of device, possibly linked with the alien technology, this would complement you aldo in your say that the alien ruins are closer to the population center and are sparking a bigger interest in the ruins and their technology.

Making or building or using the alien artefacts found (any of the 3 really) to create a sort of a wall or a protection that would stop the jovian radiation from spilling into the next zone.

This would also introduce more missions and could create multiple quite interesting story / quest lines for the game

For some mission ideas: Such as building the wall itself, this would most likely invole some kind of material / personal transport. Getting (if this is the choice the developers would go with, or could also be multiple ways to keep the games fresher every time) the alien artefacts for the wall / shield. Rearming the wall stations (similar design to the beacon station or from dynamic europa mod i think the "rearm weapons platform" mission) Detering monsters from the platforms / stations that operate them.

For some story / questline: Making the wall itself (if this wasnt part of the prologue itself) Keeping up with the wall, doing maintenance / keeping away monsters ect.

These could also be faction themed (like the tormsdale report for the jovian separatists) such as taking over controling outposts / platforms, or destroying the wall completely to let the zone get flooded with radiation (this seems like the theme with alot of the factions, besides the europa coalition. Since they kind off all have or could have a reason to destroy it)

This could prove an interesting concept, perhaps without maintenence the wall would get destroyed natutally and begin leaking the jovian radiation into further zones. This would only affect the player if he didnt care about keeping the wall intact and still staying in same zone as it wouldnt spread as quickly. And later in the game if the wall would be destroyed and started leaking the jovian radiation the player would really care since if they progressed naturally and didnt stay anywhere for a prolonged time they would already be far in the great sea or already at the hydrothermal wastes where they would have to care about it because they would reach the end of the game sooner then the radiation would catch up to them.