Aren't there fewer IVU's by far than IV? Couldn't you just make your HUD do something like:
IAmInvis=3,2,320,124,255,0,8,${If[${Me.Invis},${If[!${Me.Buff[Invisibility to Undead].ID} && !${Me.Buff[Improved Invisibility to Undead].ID} && !${Me.Buff[Invisibility versus Undead].ID} && !${Me.Buff[Perfected Invisibility to Undead].ID},INVISIBLE,VISIBLE]},VISIBLE]}
And any other IVU's along with those && checks.
Another option could be to add a couple of both DownShit & HolyShit entries, 1st of which checks if a global bool var (say, MyIVU or whatever) is defined, and if not, define it globally. The 2nd of each set would then check for any IVU type effect/spell and set the var to true or false, then you can just have the hud check that one condition, i.e.: ${MyIVU}
Lastly, adding those 2 items to something like MQ2Krust, so you can have like: ${Krust.Invis} and ${Krust.IVU} would be easy, I would just need a list of all the buff effect names that would correspond to each. I don't really have time to research to that level.
htw