Which means that Harumichi is a temporary pairing for Takeuchi initially and making Harumichi permanent is Ikuhara's idea, so Harumichi being permanent in the manga and anime is thanks to Ikuhara.
Takeuchi wants Haruka as a part of Usagi's harem.
I think this might mean that Seiya and Galaxia are attempts of Takeuchi to write Haruka again.
I remember really long ago, there were rumors that Haruka was originally planned to be male and not a Senshi but a Tuxedo Kamen-like character and her first scene of her donning a mask and cape are remnants of that aborted idea.
Michiru, in Infinity atleast, is simply a polar opposite to Rei -
Both have divination powers,
Rei manipulates fire while Michiru manipulates water,
Rei is Japanese culturally coded while Michiru is more European culturally coded,
Rei is the definition of Asian beauty - long silky thin hair while Michiru represents European mature beauty - her mid-length wavy hair with her forehead exposed giving an air of maturity.
Apart from the opening scene of Haruka hugging Michiru from behind, there isn't allusions that they are a couple in Infinity and can be yet another yuri fanservice.
It's possible that Haruka was meant to have a unrequited love for Usagi and Michiru was just her 'companion' of sorts.
It's also highly possible that both Michiru and Haruka were envisioned to die by the end of Infinity - Takeuchi wanted to kill off the remaining Inners in DK, Pluto (who wasn't considered a main character in the 90s anime by R) was likewise given the greenlight to be killed off after having an unrequited love for Endymion, it's not far-fetched that Haruka - when conceived - was planned to have a similar fate but the popularity of HaruMichi disabled Takeuchi from killing them off and making the Usagi X Haruka storyline impossible.
In the manga, up until Dream Haruka is in love with Usagi - all of her actions point to that.
The lyrics of Initial U are explicit -
I threw the white petals (Usagi) into the sea (Michiru)
Aiming for your shadow, I continue speeding forward
I'm entangled by your sweet hair
Your closed eyelids from that night are burnt into my mind
What I left on your lips is proof of my promise (UsaHaru kiss)
If I continue to run towards the end of the daylight
One day, your initials that you carved into my heart will shine of silver (= Usagi)
Why did you let go of my hand?
Your dried-up tears hold pieces of my dream
I let the silver mirror (Usagi) wash away into the ocean (Michiru - consolation prize)
Thus the future was decided upon
One day we'll get to be in each others arms again
I still believe that such a day will come
What I left on your lips is a kiss of promise
No matter what darkness may await me beyond the daylight
The Initial of U that both of us carved into my heart shines of gold
Haruka is basically saying she'll forever wait for Usagi and only Usagi dwells in her heart - no wonder Ogata would refuse to sing the song...