Not to yuck anyone's yum but I think the whole bloodymary dynamic is so much more interesting if its unrequited. Not 'unrequited but not really'. Not 'unrequited at first but one of them comes around' but like genuinely unrequited, full stop.
Simon is saved and shown a level of kindness he's never seen before and learns Grace saved the stars and falls completely head-over-heels and pins his entire sense of safety and self-worth to being liked by Grace. He loves him but in a way that is genuinely harmful to himself
Meanwhile Grace is serving aroace 'no thank you' realness and is absolutely terrified at the idea Simon might be falling in love with him because he does not want that kind of pressure from the one other human around. He's gotten used to living on an alien planet and living his best aroace life without ever actually doing the self-discovery to work out that label for himself and now there's another human around he's actually having to put in the legwork of working out who he is. He's gotten used to framing his societal value in a non-human framework and now there's someone else around painfully reminding him that under any other circumstances he would need a romantic relationship to have any of that.
I know you want them to fuck but βοΈ consider the character potential of them not doing that