Hey! Actually good question, originally harem is the "golden route", but i don't exclude solo LI's ending after final release or earlier! :)
Well, rest assured I'll be following the project closely.
I hope you don't take the following as disrespectful, but rather as feedback from an AVN player. I've seen many different approaches to romance systems over the years, from harem-only games to projects that successfully combine both harem and exclusive romance routes.
Personally, I think the latter is one of the best options a developer can offer. I completely understand that creating separate story arcs and endings for each route takes a great deal of time, effort, and probably a larger budget as well.
On the other hand, it also appeals to a much wider audience. Players who enjoy harem routes can experience the game the way they like, while those who prefer committing to a single love interest can enjoy it just as much. A combined system allows both types of players to experience the story without feeling limited by the relationship structure.
Whatever direction you choose, I wish you the best with the project. It definitely caught my interest.