Does the triune God have will by nature, or by persons? Given the triune God, one nature and three persons, do they experience their will in their singular nature or in their separate persons?  That is, do they share one will, or does each have a separate will which is in perfect harmony with the others?

What have published commentaries said on this subject?
While I'm not 100% certain I understand your question. If you're asking what I think; Jesus implied that the will of the Father, Son, and Spirit are separate, as He spoke a lot about the Father's will.

John 6:40, NIV


  For my Father's will is that everyone who looks to the Son and believes in him shall have eternal life, and I will raise him up at the last day."


Luke 22:42, NIV


  "Father, if you are willing, take this cup from me; yet not my will, but yours be done."


John 6:39


  And this is the will of him who sent me, that I shall lose none of all that he has given me, but raise them up at the last day.


So I think Jesus clearly implied that He had the ability to disagree, but He chose to do the will of the Father. 
I think the clearest statement of this is in John 8:27-29, NIV


  27They did not understand that he was telling them about his Father. 28So Jesus said, “When you have lifted up the Son of Man, then you will know that I am [the one I claim to be] and that I do nothing on my own but speak just what the Father has taught me. 29The one who sent me is with me; he has not left me alone, for I always do what pleases him.”