Hustini, my big brother, my beloved, why you do this to me?
Vidal is a player that not so long ago was rater at 60-70mil, not too long ago we wouldn't have traded him even for the Mount Kilimanjaro.
He's a highly rated player even amongst the players, he is still respected and looked up to by his teammates, and he is going through a slump. Discarding him due to his slump will send a horrible message to the rest of the players, it will the show that the club won't be able to stand by you in hard times (unlike what has happened with Pepe, which was beautiful). Not that long ago Pogba was talking about this team being something like a family, all of that can be torn a part by the management by deciding not to stick with Vidal.
On the field, Vidal that is horribly off form, is being deployed as an offensive midfielder. His passing has been pure shit, and yet we still play him up there. There is a problem. It's not working then change it! Heck even bench Vidal if necessary until his position is available or he is able to reclaim his spot, but you seem to straight up want him out. And that's unreasonable to say the least, and it will inevitably have negative repercussion upon the club future relations with out future stars (Pogba, Morata), they'll see what has happen to the last star in his time of need.
And even if we do sell and get a substantial amount, that amount will hardly get us a noteworthy player that will push us up, the same way Vidal has pushed us up. Players bounce back, and Vidal still got lots of fight in him, he'll make it back to the top.