Sounds very much like the situation where I was not too long ago, but slightly different. After I gave my iPhone 4 to my dad (whose iPhone got stolen), I had to make a decision - I had no phone, but only Nexus 7. I was waiting for Nexus 4 to be available, but it turned out to be quite a long wait. So I had a couple of weeks without phone (used GrooveIP on Nexus 7), then got a dumb phone just for voice calls and text messages. I left all "smart" stuff to Nexus 7. Just as how things usually turn out after my purchases, right after then Nexus 4 got back in stock.
Thankfully the expenses on the dumb phone was minuscule and now I am settled with N4/N7.
So if I read your situation correctly, you'd like to use Galaxy Nexus for voice/text (and perhaps tethering), while doing "smart" stuff on iPod, correct?
Then the obvious question becomes: Why not iPad mini or Nexus 7? The answer I presume is portability, but won't you eventually upgrade your Galaxy Nexus some day? Be that iPhone or some other Android phone.
Which OS do you see yourself prefer in the future? If you see yourself getting a future iPhone, I suppose your plan can work out. (even then, I would look at a tablet option) If Android is in your future, then I'd say dump the Galaxy Nexus and get a Nexus 4.