My idea for a solution: When a party member enters combat, force everyone within effective range into Time-Based mode, and into the combat initiative queue at the top of the screen. Even if out of combat, everyone within effective range of combat should adhere to the laws of time dilation and queue order.
+1 Party members who don't initiate the combat can obviously stay stealthed and maybe even participate in a surprise round.
If any party members are outside the "effective range", then they enter initiative (rolling for it=don't automatically get an instant free turn) the moment they enter that range. Additionally, this combat bubble should be large enough that you can't attack enemies while outside that range.
