I was thinking, wouldn't it be kinda funny to read a "stallion isekai" type, except where the hero can't get the harem? Like, he tries the routes like he expects, but the women are real instead of stereotypes and don't react the way they did in the game? Like, a comedy of errors type. Or he's attracting the rival guys instead, and he's straight.
I can't think of a setup for a harem where the MC then fails to achieve it - it'd be kinda trope deconstruction-y.