I th8nk adding the core of game world's foundation first is the right call...
And that takes time, no worries.
So, to me at least, that'd be the basic gameplay systems, plenty of girls to interact with and lewd, and farming/foraging/fighting. That's already plenty of work.
As for addons, maybe do a poll for one or two items after every couple of builds when you think you can fit it in.
And yeah, I love farming sandbox hentai games! So good stuff!
Also, incest is wincest! The more family member heroines, the better!
The shy succubus is funny tho.