They had a "normal" life before . . . and, seeing them work together so easily, I can see it . . . the problem is all the emotional drop-offs they'd be skirting.
Meanwhile, I have another song suggestion for Jack/Irina - "Possession," by Sarah McLachlan, which includes the lyrics:
Through this world I've stumbled
so many times betrayed,
Trying to find an honest word,
to find the truth enslaved,
Oh you speak to me in riddles and
you speak to me in rhymes
My body aches to breathe your breath,
your words keep me alive,
And I would be the one
to hold you down,
kiss you so hard,
I'll take your breath away
and after I'd wipe away the tears,
Just close your eyes dear
Especially the reprise on Fumbling Towards Ecstasy . . .