I think we might need a change of tac with this
If indeed Ross doesn't like Koeman, and that's the big reason he doesn't want to sign, then how about we offer him a five year deal and then say we'll loan him out for a season to Newcastle/West Ham etc?
Koeman doesn't stay that long at clubs, and it's conceivable that he might get offered another job if we do well this season
Present it to Ross as a way to get a year away, but still play regular football, and when he gets back either Koeman will be gone or a year apart will give space for things to cool down between them and they can then start anew
Seems like a reasonable compromise to me