Here goes:
I ran into this template about a week ago when trying to find a use for a third-party feat* and then gave up because of the Planar Commitment. This thread, however, got me to rethink some things.
Some dictionary consulting later, I've found a solution. But first, because if I start by saying it everyone will shout, "No, that doesn't work!" here is my reasoning:
Planar Commitment makes it impossible for the creature to "leave" the plane. They "cannot leave." Now, petitioners that can create their own functional duplicates are all well and good, but not every Petitioner has "spells," and not every DM will rule that "spells" is Ex or a "normal" ability. So how do you let the Petitioner go elsewhere without leaving? Well, let's deconstruct "leave." To "leave" a place, one must go out of that place. I don't have an OED subscription anymore, so I'm going off of dictionary.com, but I think we can agree on the reasonable definition #1: "to go out or away from, as a place." Now, to "go" is simply to move or otherwise be transported. Let's look at "out or away from." Well, to be "away from," you must not be in the original place. To be "out" of the original place, you must not be in the original place. A few of you are grinning already. That's because a few of you are thinking with acorns. Enter the Acorn of Far Travel. Give this wonderful acorn to your Petitioner and he'll be good at PLANES-HOPPING. People will look at your petitioner and think it's NOT A PETITIONER. They'll be wrong, and you'll totally PETITION THEIR ASSES. You get the point.
So, yes, I am suggesting that this actually has a purpose. Why are we giving acorns to petitioners? Do we simply want to wreak havoc on the material plane by transporting allegedly CR 1 Hecatoncheires to small towns or, hell, big towns? Maybe, and is that so wrong? I mean, the little fellows come with a maxed-out 16 hit points and the capability to make 100 attacks against big enough targets (sans greatswords, oddly enough). But some of us have other dreams. Some of us have DMs who like a challenge, or like excuses for cruel and psychologically unstable retribution, or just plain don't know what's happening because we roofied their soda for him giving me the Girdle of Delicacy (+5 Dex, makes you female) in our loot session after I saved the party's collective asses from three red dragons. And for those of us, we can turn to the 3rd-party Netbook of Feats, which has a feat that is problematic enough on its own and even better now that we've created CR 1 godlings. Ladies and gentlemen, the Enchanted Familiar. The Enchanted Familiar is any creature of Diminutive, Tiny, or Small size whose CR is 1/3 or less of your level. Now, yes, I may have led you on with Hecatoncheires. He's far too big (that's what she said). But what about a Will-O-Wisp for starters? Demilich is awful because it lacks any meaningful abilities to retain, but think of the possibilities. Moreover, if your DM is being lenient, is it too late to mention that while we took pictures of him passed out with penises drawn on him that we realized we could add templates to the creature before it becomes a Petitioner and handwave it all in our backstory? Oh man is Derek in for one hell of a surprise.