Just remember: the cursor wont be translated into the spot shown by the video feed, repeater is still going to work like before just with the video feed showing

A Click Bar might be more appropriate than a repeater region, since you can tell it to do whatever you want when you click (e.g. fire off a spell in that window), and can do different combos. A repeater region would require something right there in the other window

The other question is if it's possible (and if it is, how) to make it so:

1) A step will only move to the following after a specific amount of time;

and/or

2) A step will only move to the following after the macro within it has done its full cycle (that can for example consist of a 4 spell cast sequence).
1. there's a checkbox at the top of each Step when setting up your Mapped Keys, which says Do not advance. That's what this is for

2. WoW does not provide or allow a method to receive feedback from a castsequence or cooldowns, so you will need to plan accordingly (when estimating for "Do not advance", for example)