Don't know if this would fit the bill or not, but here's an idea:
You could mod a raid window to keep an updated "HoveredPerson" variable in it.
You could also put in bits of code that access that variable that can be called from a macro, like EQAditu does in his Hotbar Macro Scripting.
You could then have hotbar macros with lines like
Code:
Macro1
/show_window MainHUD.Raid.CureHovered
Macro2
/show_window MainHUD.Raid.CureCurseHovered
Macro3
/show_window MainHUD.Raid.WardHovered
Macro4
/show_window MainHUD.Raid.HealHovered
You could then bind these hotbar slots to any spare mouse buttons or keyboard combinations you desire. You can't override the default actions of left and right click, but if your mouse has extra buttons you can certainly use those.