It's interesting to see people are a bit underwhelmed at Koeman and de Boer et al, which goes to show how expectations have changed.
If you're looking for a magic wand appointment you won't find one, they've all been taken. Mourinho, Guardiola, Conte, even Klopp (honeymoon over) will all be expected to guarantee success this season, which is by definition, impossible because they can't all win it. So therefore, there is no easy fix.
Looks likely that Wenger will continue at Arsenal. But if Wenger did leave, the favorites for the job are as follows 1. Koeman, 2. de Boer, 3. Low, 4. Mancini. Looking down the list, it's hard to think of a standout, realistic candidate for them.
Just for some perspective.