So for story no posting order and for combat there will be a posting order based on initiative. You will have 48 hours to post combat before I will decide that you are either skipped or I may treat it as a critical fail and you end up falling down or something.
Anyone who is opposed or has questions/ideas feel free to speak up.
No posting order during out-of-init scenarios is preferable for me, as long as people allow others to get words in as needed, etc, per standard RPing etiquette.
One thing I've seen done in combat for those who don't post on time is to have the character attack the nearest enemy (or use a cantrip if a caster, preferring their previous target if it's still alive). This means the party isn't punished for one individual's mistake, but it also means that the individual doesn't have to track spells or resources they didn't know about or plan on. If that individual ends up being our cleric, sometimes forcing a Cure Wounds or Healing Word when it's obviously necessary (someone is dying, for example) might be preferable. Having only a critical fumble might hurt the rest of us more than them.
48 hrs is a reasonable amount of time, in my opinion, to wait for combat. However, I hope that we can post quicker than that the majority of the time, as combat is intended to be fast-paced and reactionary rather than something we can plan a full week for. If we have 6 people in the party (plus the DM) and we take 2 days between each post, we'll have 2 weeks for a single round of combat. If we can get multiple posts per day, that would be preferable for all involved.
Do you want us all to post individually for our rounds in combat, or would you prefer to have a DM post where we OOC / PM you our preferred actions and rolls and you add the info into the single post? The latter is much faster but has a lot less creativity (and therefore GLORY!). In either case, having the fighter say "And I attack this guy. And I attack that guy." can be boring for all involved unless we're allowed to add a tiny bit of flair into our posts (as long as they aren't mechanically broken).