So how about doors for the houses? Maybe being able to close/lock the back door? My house has two rooms... could be useful to be able to leave the front open for guests and the back half with my stuff.
Fences... something we can pen the animals in.
A Front Yard type space would be a big addition. Even just being able to define 'your yard' and decorate it a bit would be huge.
Side note... I was really disappointed to find out I couldn't release fireflies into Ani's house. I thought they would have gone great with the festive atmosphere.