Well, darn. Sorry to hear it. Are you really interested in tossing your cards in the air and rethinking the entire layout, though? That seems a little extreme given its excellence. If you aren't, at least you very fortunately HAVE a less dramatic solution and can leave the refrigerator just where it needs to be.

And, happily, broom closets don't have to be deep or wide to be functional, right?

That's too bad; I like the location of the fridge where your plan shows it for a number of reasons and it looks like a good layout (tho I'm no expert.)

How much would it cost to move the stack? And would it require a renovation of the bathroom above the kitchen?

Since you're paying for a kitchen renovation anyway, which we all know isn't cheap, I think if you didn't pay the incremental fee for moving the stack and ended up with a compromised layout you would regret it. I say this, though, not knowing what it would cost and whether the whole stack straight up has to move or whether it can be angled enough above the fridge to come down the rest of the way in the broom closet space.