Possibly not completely relevant unless using Inform 7, but there is an extension in the Public Library for this type of thing if it helps anyone either outright or for study with aims toward rolling their own:
Variable Time Control by Eric Eve (Version 4). Allows individual actions to take a different number of seconds, or no time at all. Also allows the standard time taken per turn to be defined as so many seconds, which can be varied during the course of play.
(Alt link since the extensions on the original website are currently out of order)
https://i7el.herokuapp.com/extensions/variable-time-control-by-eric-eve
(All I7 Extensions have their own thread, though there is currently no discussion in this particular one.)