I think it is completed and won't be touched anymore.
Reona path is still not completed.
Probably a question of "how to get there slower". Avoid having too much sex with the girls in too quick succession, so the event does not trigger before you are ready.
In addition to what has been said about wiki and in game hints: a classic walkthrough does not exist anymore and basically does not work that well for this kind of game, so it is unlikely somebody will do another one.
While that would be nice, if the "marrying a girl" should have any impact on the story at all apart from "you and your whatever harem tied the knot" in a stats window, it would need a shitton of if-thens and new content to be added, which would then probably only be seen by a small part of the playerbase. I am not against the idea, I just don't think it really is feasible.
Last time I played you couldn't marry her or get her to agree to want to have kids. Has her story been 'completed' since then where she will actually marry mc?