And maybe the quality of the treehouse would depend on your sims handiness skill as well? I.E a sim with a low handiness skill will end up making a really shabby-looking treehouse while a sim with a high handiness skill will make a better one. Also, you can 'upgrade' it in similar ways to how you can upgrade electronics, like adding a slide, tire swing, etc. Sims with the mean/evil/hates children traits can sabotage the treehouse, and treehouses of poor quality are more likely to just fall apart alltogether.
And with the release of seasons, storms and blizzards are also likely to destroy your treehouse.
tbh I just really want treehouses. Even if we can't actually use it, I would at least like for someone to convert the treehouses from Generations to the sims 4 for decorations.