The issue you're identifying is that a randomized turn sequence discourages planning amongst players...because there's no way to know whether Beryl the Barbarian will get to act before or after Sam the Sorcerer's fireball. It's not impossible to plan, it's just much harder due to randomized turn sequence. This is ONE of the reasons I often see player strategies go haywire once combat begins (yes, there are other reasons too).
Last time I played in person I adopted a much more casual simple version of what you are considering... I call it 'clustered initiative with a football huddle.'
Initiative is determined as normal, with 2 exceptions: (1) players who want to go at same time roll one die using the lesser of their initiative values; (2) players who have consecutive initiative rolls with no monsters between them can act in any order they please. This creates 'clusters.'
Then, unless the party is surprised or the players clearly just want to get to the fighting, I give them about a minute to come up with their approach now that they know the initiative order/clusters. This is the 'football huddle.' At the table the "timer" is really just me setting up maps/minis, checking my notes, answering quick questions, and so forth.