Great topic, i didn't wanna launch myself into it before i relistened to the majority of Lacrimosa this week, and also before i was rested and had time to think properly about it ^^
There's no particular order in my lists, except for the first 1 or 2.
So, the songs i would like to hear live if anything was possible would be :
Sanctus (my favourite Lacrisong ever by now, objectively, if you see what i mean

)
Strasse der zeit
Hohelied der liebe (would be so awesome!!! XD but so impossible xD)
Make it end
Warum so tief
Flamme im wind
Deine Nahe
Einsamkeit
And then the usual :
Der morgen Danach
Lichtgestalt
Alles Lüge
Halt Mich (drums indeeeeed, Liv xD)
Turning point
Feuer would be pretty cool, and i guess quite possible

same for Mantiquor?? ^^
and maybe Alleine zu zweit and Ich verlasse euch dein herz, i used to love them, though i dunno how i would appreciate them now, as i have associated them very strongly to some situations in my life that i now left behind me... (so much passed since i started to listen to Lacrimosa!! O.O)