OT: Another analytic question

Another question regarding analytic or isolating
languages. I know very little about them, but one of
my current conlangs seems headed in that direction.

What I'm wondering about is it seems like most
analytic languages rely heavily on word order to mark
roles, as in SVO, SOV, etc. What I have in mind is to
always mark every part of the sentence with a particle
so that word order is irrelevant to meaning and can be
used to emphasize some part of what is being said.

For example, suppose I used the particles "su", "ob",
and "indo" in the sentence "Su John gave ob book indo
(to) Mary." Now I can shuffle the pieces around
without confusing the roles of the various players and
write: "Indo Mary gave ob book su John." or "Ob book
indo Mary gave su John." "su John" always tells us
that John is the subject no matter where "su John"
appears in the stream of words that makes up the
sentence.

Are there any analytic natlangs (or conlangs) that
completely mark the roles of the participants so that
word order is (relatively) free? Or am I venturing
into unexplored (or unproductive) territory?

--gary

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