I've done pretty extensive testing this weekend and I'm happy to say that the FTL system utiliziing /click for easy changes in group composition works well.

A few comments:

1.) I use shift as a modifier to spells. The FTL system seemed to breakdown when trying to include rshift in the FTL definitions when combining with macros that were called through shift. I know use ralt, lalt, and rctrl for my FTL modifiers which leaves shift for spells.

2.) I use mouseover healing and have not thoroughly tested this system use in targeting friendly units.

My two target macros:

When using the priest, moonkin, moonkin, pally, shaman group:
/targetexact [mod:lctrl,nomod:ralt]Grouser;[mod:lctrl,mod:ralt]Owltoîd;[mod:rctrl,nomod:ralt]Owltoïd;[mod:rctrl,mod:ralt]Stróng;[nomod:rctrl,mod:ralt]Curiously

When using the moonkin, moonkin, moonkin, pally, shaman group:
/targetexact [mod:lctrl,nomod:ralt]Owltoìd;[mod:lctrl,mod:ralt]Owltoid;[mod:rctrl,nomod:ralt]Owltoíd;[mod:rctrl,mod:ralt]Stróng;[nomod:rctrl,mod:ralt]Curiously

Eventually I'll have a target macro setup for my 5x moonkin group

An example spell macro is:
/click BT4Button120;LeftButton
/assist [noharm]
/castrandom Wrath, Wrath, Starfire

For follow:
/click BT4Button120;LeftButton
/follow

I can't remember why I need the [noharm] and that may have been included when I was trying to fix the shift-modifier problem (in other words it may not be needed anymore and may actually be screwing up helpful spells, but since I use mouseover healing I haven't really screwed around with it).