Drunken suggestion:
1. Random generated terraforming quest.
Once player makes his first successful terraforming of any kind, there are probability of generating BBS quest for terraforming a random fully surveyed non-colonized planet into a specific (usually Cat3) type. No time limit, but player not able to accept more than certain amount of that kind of quests. After a successful transformation planet is transferred into control of faction, who gives a quest. Player get payment based on colony size, built structures cost and any additional equipped remained (Ai cores, NF, ST or else). As an additional reward - reputation gain over a time, like +5 each month for a one or two cycles.
2. Random generated station construction quest.
Mostly the same, but trigger is building a specific type of a station (mining station, siphon or gate). Success criteria - station has to gain a size, determined by a quest. Then it is transferred to a customer's control.
3. Recolonize quest.
Sometimes worlds decivilized because space is cruel. Sometimes, because player is cruel. Mission is to recolonize abandoned station and rise it population to certain point. Of course, that abandoned station should exist for quest to be generated.
EDIT: If reward is not enough you think, that could be a unknown blueprints or unique, other way unobtainable, ships.