Anyone else think that it could be possible?

Well, practically anything is possible, even the stranger being us from the future, but I don't think this is likely.

We know that the stranger is from the future and seems to know something about us.

For instance, she could be just someone who has knowledge of the forest, something that is true for Osiris, spoke to Saint-14, whom seemed to have travel to the future (we supposedly give him his shotgun), is someone from the future or maybe something else entirely.

I also dont remember the stranger ever referring to herself as a guardian either.

I don't think she does, but one of her lines is supposedly "No, I was not forged in light. But I believe where our paths cross, ground could break." (too lazy to make sure Destiny.wikia is 100 percent accurate), which makes even less sense if she is a ghost. I mean, that is about as literal as you can be with "forged in light."

The fact that osiris refers to her as little light and the stranger refers to ghost as that.

As for this, I would say it's just a tongue-in-cheek sort of deal. At most, she might've met Osiris and picked up his mannerism, over being his little light.