I share the Koeman skepticism long-term. I think he's a solid manager and a safe pair of hands, but I don't see him as a difference maker or the kind of manager to bring about significant over-achievement through tactical innovation or exceptional player development, which is what would be needed to trouble the Top 6 consistently. He was a reasonable choice for the time but we need a more progressive (and potentially risky) appointment next time.
I'm quite looking forward to getting into a more frequent coach / manager cycle.
I like Koeman, principally because I appreciate getting the basics right first and foremost.
I think he does try things tactically to lift us beyond the norm, they just don't work all the time...

But yeah, until result bear out the safe money is on solid, if unspectacular, performances / seasons.
I think our signings have been good in terms of they should be fairly adaptable to most tactical approaches which should be beneficial in a changing cycle.
Re risky appointments I would hope that if we're still showing signs of promise, being close to top 6(4) etc that with the wages that we offer we should be able to attract someone who at least should be good, they might not be guaranteed to get us further than wherever Koeman leaves us but we shouldn't be risking Martinez levels of uselessness.