What you relate about military grants is interesting.
However, when you say: "Thomas Isbell; III 486, assigned by Hardy Alway, Pvt. (W. B. says assigned by heirs of Hardy Atway) III 732, assigned by Arthur Smith, Pvt. III 736, assigned by heirs of Abraham Duoster (or Decoster) Pvt."
--in each case, Thomas Isbell purchased the Land Warrant or grant that was issued to others --to Pvt. Hardy Alway/Atway's (or his heirs) --to Pvt. Arthur Smith --to Pvt. Abraham Duoster/Decoster
So none of these items had anything to do with military service of a Thomas Isbell.
This not to say that this Thomas Isbell did not serve, or that he did not receive Military Bounty Land by virtue of such service.Just that what you present is not related to his own service.