You really think that in a busy dungeon with multiple slept mobs, that the single-entity focus frame is going to help? That is a secondary focus, for you, and only you. It is not meant to interact with the rest of the party, with who you should be communicating via the mk/marker system.
Do what the rest of us do - please use the markers, which also informs the rest of the party what you're up to, and tells them to both avoid going for CC'd mobs, and informs the mages to avoid AOE's from waking them up.
Just my personal opinion, but adding what you want is not really needed. If things get busy with multiple mobs you are CC'ing, the personal focus frame doesn't and cannot provide anything to quickly respond in the manner you described. There are tools to do this, markers, assist, <tt>, all neatly tied into a marking system.
The only problem uncovered so far which relates to this is how to track focus on a tank which isn't marking. There is a way to do this, but it's a cludge, but eventually as the lvl's go up, everyone is using markers. This has nothing to do with the focuslist as such, just an example of perhaps the confusion between what is traditional focus as per all the other MMO's, vs. that focuslist command which SE has provided. How you described focus is not what that focuslist feature is about; it is your own personal, and I can't stress this enough, secondary focus. Nobody cares about secondary focus, well ok, apart from you and maybe 2 other people :)