I fully agree, it is better to build a foundation on which you can build a castle (as they say). I rather hope that he has a notebook where he writes down different ideas, for better idea selection.
Well, if we are looking for missed opportunities for later reference, then let me point out the "housework" and "afternoon tea" options.
housework: Once she starts accepting the MC, have her offer "Ye Olde Naked Apron Play" while she cooks. She could be teased into eventually having sex in the kitchen wearing only an apron.
Afternoon Tea:
It could be an alternate route to getting her to accept sex, or an additional requirement, that the drunken play leads to sex.
Once unlocked, it could lead to scenes where they have drunken sex, where Chiho would be more of an active participant as opposed to a passive receiver.
It could lead to a mini-game linked sex scene too, where they break out the Wii and use a "naughty" feedback toy linked to the game for Chiho. Or something similar. The higher scores will unlock more scenes, where things get crazy.
These are easily extended in a known way already used, and will add new life to currently dead options