I do not think I understand what you mean by 'signal to an Indicator running on a live chart that it wants a wait time'. I have tried using the code below in a couple areas such as OnTick and before the lines of code that fill the buffers for the indicators that I use
Sleep() does not work in the Strategy Tester.
OK, I should have said create an EA or Script, Indicators shouldn't sleep . . . and run it on a chart, any chart. It watches the Global Variable that your EA running in the Strategy Tester writes, it writes a 1.0 when it wants a delay, and sits in a loop waiting for the Global Variable to change to a value less than 0.5. The EA/Script sits in a loop looking at the Global variable and when it sees it go above 0.6 it waits a predetermined number of seconds ( Sleep(number_of_seconds * 1000) ) and then sets the Global variable to 0.0 . . . the EA in the Strategy Tester will see this and then resume running . . . it has been delayed by number_of_seconds . . . which is what you asked for.
I have coded this before in mql4 and it works . . . you can try it in mql5 and let us know how it works for you . . . by the way, if you use a Script you won't need ticks . . .