One possible storyline could be how they deal with the challenges of impending parenthood while still being involved in the galactic struggle. For example, they might have to find a safe place to raise their child away from the Empire's reach.
The pregnancy might change the way other characters interact with them. Allies could be more protective, while enemies might see it as a new vulnerability to exploit. For example, the Empire could try to use the pregnancy as a way to blackmail or manipulate them. It also gives fanfiction writers a chance to explore different aspects of the characters' personalities as they adapt to this new situation.
There could be. A lot of fanfic writers come up with really creative crossovers. For the 'harry x leia fanfic', you should check the reviews and ratings if available on the fanfic platforms. That way, you can quickly narrow down to the ones that are more likely to be good reads.
One common theme is the depth of Leia's love for Han. The fan fictions often show how this love doesn't die with Han, but rather transforms into a deep - seated grief. Another theme is the struggle to move forward. Leia has responsibilities, but her grief over Han makes it difficult for her to fully engage in her duties.
One of the great Han Solo novels is 'Han Solo at Stars' End'. It really captures his roguish charm and his adventures in the Star Wars universe. Another good one could be 'Han Solo's Revenge' which shows his determination and cleverness in different situations.