it's interesting you bring up ownership of the body... but why just the body? If we're talking about ownership as meaning having total control over something, then we don't own ANYTHING or anyone, for that matter!
You can't guarantee you'll have the shirt on your back tomorrow, or your house, your favourite cup, your dog, your leg, your health, your money, your friendships, job..... and on and on... all these things will break/die/get lost/stolen or decay.. and that's largely out of our control.
But I think the real point of investigating 'owning your body" from a Buddhist perspective is what others have mentioned, coming to negating the existence of an "i" that owns the aggregates that make up what we call our body.
i definitely agree with this. i think in the sense of ultimate bodhicitta investigating the idea of ownership will always come down to the discovery that there is nothing to own and no one to own it. also, as konchog1 pointed out with the quote they posted, looking into ownership of our bodies can also help with developing relative bodhicitta as well. once we have taken the bodhisattva vow, we are supposed to look at our bodies as an invaluable tool for helping others. we are to be unattached to our bodies, but we still take good care of them so that we have a sound vehicle for benefiting other sentient beings. in that sense, too, we don't own our bodies to use in whatever way we want, to accomplish our own selfish benefit. it's a good meditation point, for sure!