Palace usually approach the signing of a new manager the same way as a new player: Aim as high as you realistically can, which means aiming for someone who might realistically hope for a bigger club than Palace.
The alternative is to settle for someone unproven or less impressive. The downside is, it usually requires us to wait whilst the bigger clubs put their affairs in order, just so our target knows he is not part of those plans. The potential reward might be an impressive arrival that makes a difference. The risk is that we get strung along (Nuno) and end up with a last-minute compromise.
Once in a blue moon it is possible to agree in advance with an out-of-work coach who happens to also be first choice, like Glasner. Mostly though, we have to play the game.
I don't expect Palace have got anyone lined up yet. As nice as it might be for the new man to have a say in signings, we use the director of football model. That doesn't suggest that we think we need a coach in place before we can make sales and signings. Not that I expect us to make signings quickly, either: See opening paragraph above.
Add in the World Cup delaying things, and I see little reason to anticipate early arrivals in the dugout or the pitch.
That said, there are reasons to think we might be sorted earlier than usual this time. (Firstly) we knew Glasner was going and so have at least had time to identify our preferred candidates; (Secondly) most of the big boys happen to have made their appointments early this year; (Thirdly) some of our apparent options are out of work at the moment.
Even so, if there is any truth at all to the reports that we have prioritised someone like Iraola then he'll still have some other, bigger options and we will still have to wait for his decision.