I'm working on finding a way to do this a bit better, but haven't had much success yet. One of my problems with macros and clicking/hovering is that I can't move very well while I do it (becomes pretty important in some fights where getting in/out of line of sight quickly is important). For fights like Gehennas, it's easy enough to do something like this (and a good solution, actually), but there's got to be a better way. People are already finding work-arounds to some of Blizzard's new restrictions, so time will tell if we can ever recapture even a portion of Detox/Decursive-style behaviour...
In the meantime, though, this really is a good idea...I always overlook the mouseover targetting for some reason when I'm playing with mod coding. I'll have to take another look to see what other functionality is in there that I may be overlooking. Gah, if only there were more hours in the day!
As for displaying all 40 players without cutting into the screen too much...welcome to a healer/raid leader's world I have very little actual "display area" where I can see the fights while playing Verissi (even less when I played a paladin) because I need to see things like health/mana levels, buffs, debuffs, etc. I used to shrink the boxes to give me more room to see what's going on, but I found that I was straining to read names and couldn't do quick-glances to see how health/mana were doing. I fixed some of this by having the boxes recoloured if certain conditions were met (debuffed, afk, etc), but sometimes I need a bit more detail than the colours provide.