I am not familiar with TestPartner (discontinued, now called Silk Test). However, my suspicion is that what is running with Silk Test is some sort of compiled test so that, debugging is debugging code along side of a compiled execution run. TestComplete's technology is more akin to a script running on a web page... it is exectued as interpreted code, running in real time. There's no "compile" time so what is in the code is EXACTLY what is run, it is loaded when it is started and executed. Altering the code while it is running is not possible because the code that you see is ACTUALLY what is currently being executed...
In other words... I wouldn't hold your breath on this one.