I figure the main reason for the current system is multiplayer. If you are roaming with Shadowheart but the other player is elsewhere roaming with Gale (just throwing things out there), Player 1 gets engaged and is stuck in a fight while Player 2 can still roam the map without having to suddenly be dropped into combat mode moving 30 feet at a time with 2 separate characters.
But, the point is that breaks the system. Player 1 can literally trigger the entire fight at the goblin camp, and all the enemies are frozen in time while Player 2 can drop in behind them all and sneak into the goblin base, kill all the bosses and waltz right back out all while Player 1 is still sitting there with the entire goblin camp frozen in time.
That's a rough example, but that's my point. If you enter Turn-Based mode, the whole world should enter Turn-Based mode. If Player 2 has to wait for Player 1 to complete an entire combat, then that's just how it is. That's how it would work in a tabletop session which is why DM's try to encourage players to stay together. It's boring waiting for other players to finish solo combat, but you both chose to split up, so you face the consequences of said action.
In Solasta, it's just like this except it is only 1 player. If one character triggers combat, all characters, no matter where they are on the map, enter combat.
