I'm working on my own homebrew RPG system which I want to keep light on rules. Therefore I add only rules when they are needed. One rule which I did not use was an implementation of "initiative", where complete combat turns are subdivided into turns for each individual participant.
In combat everyone's actions happen at the same time. There is no order imposed by stats, dice rolls, or activity chosen, i.e. no initiative scores or initiative rolls such as in DnD 5e. It is more like melee from Warhammer Fantasy (the strategy game, not the RPG).
A combat is divided into turns. During each turn, all participants' actions are assumed to occur simultaneously. Attacks use a skill check with a modifier. Damage is static. Adjudication so far follows an arbitrary order. If a participant dies, this does not prevent them from acting during the same turn, just because the action killing them was resolved first.
I did like the feeling in general during playtest, however management of combat turns was very chaotic since I could obviously not do all the adjudication at the same time.
My question therefore is: What game mechanics can I use to facilitate combat adjudication without imposing an order of action? I prefer answers referencing published RPG systems. Ideally, the solution would be as simple as possible, only facilitating adjudication without posing restrictions on what can be done in the game.
The problem to solve is: How can the adjudication be made less complicated without introducing subturns for the individual participants?
Criteria for good answers:
The solution should be mechanical instead of technical, i.e. based on game rules instead of relying on online tools or similar.
Simple. The fewer rules the better.
Preferably from published material. RPG material is preferred over other sources which are preferred over Homebrew.
Non-restrictive. Mechanics are preferred that do not rely on a set of potential actions (even if "wildcard" actions are in the set)
The criteria are ordered by importance.