JMA:

Given a compliant indigenous folk with an underwhelming ability to resist, your suggestions and your multi-national force would probably be quite effective as you say:

I would suggest under circumstances where the situation requiring humanitarian intervention bring troops from many countries all across the world the word needs to be spread to any Crockett, Bowie. Boone or Carson types running around in the woods armed that the carrying of weapons for the duration will be problematic as the soldiers will not wait to be shot at but rather enforce the peace and reduce the number of weapons carried by the citizenry which could potentially confuse matters.
....
I tend to go with and thorough prep-fire of the objective followed up with prodigious levels of prophylactic fire while sweeping through and clearing the objective. Not likely to find a living thing there when you arrive.
Solitudinem facient et pacem appellant. (Tac.)

I fear I am a better Celt than a Roman.

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MAL (mon "jumeau mal" ! )

A large recent literature exists on military commisions; but that is mostly in the context of the Gitmo MCs, which are very close to formal courts-martial. Besides the 1953 JAG School article I cited above, I've found , e.g., recent articles on the use of US field MCs in the Mexican War and Civil War.

Myers, Conquering Peace: Military Commissions as a Lawfare Strategy in the Mexican War (2008)

Vagts, Military Commissions: The Forgotten Reconstruction Chapter (2008)

The use of field-expedient military tribunals goes well back in time. You might be especially interested in this example, since it involved the "Colonial Troops", 1684: Indian murderers punished by Du Luth (starting at p.114 - 12 pages; you can check out the original when you are next in Paris). This is a translation of his 1684 report, which illustrates the use of diplomacy and smarts over brute force (which "Du Luth" didn't have anyway).

"Du Luth" was really Daniel Greysolon-Delhut, who was a talented officer and above average in Canada (bios in French and English). He could have treated the murders of the French-Canadian fur traders as a native uprising or as a law enforcement matter. He selected the latter approach and did not simply execute the murderers.

From the English bio, a brief summary of this case:

He commandeered the services of licensed traders to help fortify Michilimackinac, reprimanded the Potawatomis for their lukewarm attitude toward the French, and renewed his peace-making efforts among the Foxes, Sioux, and Chippewas. The last of these nations was especially difficult to manage as was demonstrated in 1684 when four of its warriors murdered two French traders. When one of the culprits appeared at the Jesuit mission of Sault Ste Marie the staff of 12 on duty there did not dare to arrest him, fearing the reprisals of his tribe. Dulhut, as soon as he learned of the incident, hurried to the mission [JMM: with 6 troopers], rounded up the suspects, including the chief Achinaga and his two sons, and put them on trial. Achinaga was acquitted and his younger son pardoned, but the two others who had been found guilty were executed before 400 Indians. By coldly meting out this punishment, Dulhut taught the natives that the French were a people to be respected and feared.
This is a good case study in how to handle situations when your force is underwhelming.

I can see the murder scene from this room when the leaves have fallen. One of the six troopers with Greysolon-Delhut, when the principal murderer was arrested at Sault Ste. Marie (about 250 miles from here) (see p. 115), was one "Le Mire" (prenom: Joseph - one of my many TdMs in Canada).

The suggested use of military commissions in the field may well find few advocates. That despite the fact that it could provide prompt justice as an alternative to either "justice" delayed (as at the Hague; and hence, in reality, often denied) - or to shooting prisoners, which even if effective leaves no honor as recompense for the shooters.

Regards

Mike