If you set up the Infinity Engine to globally pause every N seconds in combat, it would become phase-based.
Uhm, the thread has moved on but I can't let this one pass: it would most definitely not.
Phase based would require that: a) it's impossible to pause the game outside of the "planning phase" b) it's impossible to control your characters outside of the "planning phase".
Neither the player nor the AI adhere to these restrictions in IE, so auto-pause does absolutely nothing useful (especially when the engine bugs out and pauses separately for each individual character instead of being global like it should).
Incidentally, phase based would make the best AD&D implementation because that's exactly how the ruleset works: both the players and the opponents decide which action to perform that round, then initiative is rolled (and modified by weapon speed factors etc.) and actions are executed in 10 round segments, actions falling in the same segment happening simultaneously. All the benefits of character skill deciding the outcomes and player skill deciding what actions to perform, with fast and simultaneous resolution (and pretty animations for those who like them).
In RTwP, there is no global "planning phase" when both the player and the AI make decisions, but these decisions happen at two different discrete scales: a) "how fast can you click" for individual RT orders or alternatively "how fast you can push pause to give multiple orders" to escape the need to click like a maniac for the player b) how ever often the AI is set to "tick". And the AI needs to be set to arbitrary slowness since if the "turns become infinitesimally small" as you put it in another post, the AI will be able to adjust its decisions orders of magnitude faster than any player. Imagine your worst IE kiting and mid-action switching cheese, only with flawless execution. Right.
If they really wanted people who love combat to have the option to play detailed battles while leaving storyfags unhindered, they'd implement either turn-based or phase-based combat and add an auto-battle option. While RTwP is basically starting with auto-battle (just let your AI duke it out with enemy AI while you look at the pretty animations) and adding specific exceptions the players can use when it fails on top. In other words: meh.