I mean they were probably thinking that having all of one side go before all of the other side is unfun and broken.
[...]
That's a completely false dichotomy, though. Let's not pretend that it was like that in D:OS1. Or practically any other turn-based game based on initiative.
I'm not a huge fan of it, but I believe FFGs Star Wars Imperial Assault handles initiative in a similar manner (not a huge fan of the initiative system you describe, big fan of Imperial Assault).
D&D 5e has several initiative alternatives in the DMG as well, but I can't recall if they've got one like this. I know they've got one that has one entire side go before the other though.
