Outside of us offering them Coutinho in the package, I don't see them selling to us. But we absolutely should offer up Coutinho, especially since they seem to really want him as well.
I'd even take a straight swap deal at this point, even though if we're being real, they should pony up 20-40M along with Rashford to make up the difference in market value. But in terms of skill, age and more than anything compatibility and fitting into our team, Rashford would be so much better than Coutinho that he'd be worth it, even if we gave them some extra money to make the swap happen.
Rashford brings forward versatility, a possible future Suarez replacement or LW starter, since we expect Dembele to play RW long term. So he fits two of our immediate and future needs, exactly the type of player we're looking for at this point. Not to mention his young age and insane potential. Of course the acclimation to La Liga and the Spanish language could be a big problem for an English boy, but I'm confident he could adapt in time. And since Suarez is gonna be here for a couple of more years anyway, that would give Rashford ample time to do just that in the meantime. That is, if he's willing to be a squad rotation player for a year or two. Of course, there are many obstacles, like ManU being his boyhood club, in which he's desperate to succeed and become a big star there, not to mention Ole liking him more than Lukaku and thus giving him a starter spot right now. But if he were to choose a challenge of moving abroad, especially to Spain at this point of his career, he would show some real maturity and drive for the biggest things in world football, at least in my eyes.
While the only thing Coutinho brings, is 160M on the bench/backup player. By now I'm convinced he can't play LW for us, and he's too irresponsible to play in a 3-man midfield for sure. His skills and strengths correlate too much with Messi, and since Leo is irreplaceable and will stay at the club for at least 3 more years, I don't see the point in keeping Coutinho, especially since he's in his best years now, so by the time we would expect him to take the mantle from Messi, he'd be on the wrong side of his 30s. Plus, United are desperate for another big name to put alongside Pogba and De Gea, and Coutinho brings them exactly that. And there's the ex-Liverpool thing, with which they'd stick it to them a little in the process as well. I'm just not sure Ole would allow that, he seems so much more inclined to give home grown talent a chance to succeed before having a big name player with a fat salary in his team instead. But I'm sure the United higher ups would absolutely give us Rashford, if we give them Coutinho.