Okay, after some more research and thought, I have reached some tentative conclusions. Feel free to tell me I should start a new thread instead of reawakening this one.
Unit committees are established by a charter which obliges them to follow BSA rules, regulations, policies, and guidelines.
The unit is “supervised by” and “operated under the guidance of” the unit committee.
Unit committees are boards under the definition in RONR §49.
Unit committees are not part of a society.
Committee members serve at the pleasure of the Chartered Organization Representative, and the committee cannot expel members on its own authority.
Unit committees are required to operate within the Chartered Organization's policies and guidelines.
RONR p. 486 states that "a board that is not part of a society may make its own rules.”
Therefore, per 3. and 4., unit committees can make their own rules, which, per RONR §2, would seem to include bylaws, rules of order, and standing rules.
So question 1: Should unit committees have their own bylaws?
My current feeling is that no, they should not. Of the sections listed on RONR p. 13, (1), (2), and (3) are dictated by the charter and BSA policy; as for (4), per BSA policy, the chairman is really the only officer, who can appoint or replace members in other positions at will; as for (5), BSA guidelines say that the chairman calls the meetings; as for (7), BSA guidelines establish various Roles which can be held by multiple people at once, making them, in effect, standing subcommittees.
Moreover, having bylaws would seem to imply that the committee answers to itself, which is not the case. Having bylaws when a superior organization can dictate that the bylaws be changed at any time seems out of step with the purpose of bylaws.
However, having rules of order and standing rules does seem like a good idea.
A ) "Unit committees are part of a society; they are an instrument of the chartered organization." While that's true as far as it goes, they are neither a committee of that society, nor the board of that society, and so it seems to me that the committee is not part of a society in the sense of RONR p. 486, in much the same way that a State university board of trustees is a creature of the State legislature, but is not part of the State legislature.
B ) There are things that can and perhaps should be done in the bylaws, such as
Establishing meeting days (the official guidelines only say that the chair calls the meetings, which doesn't necessarily contradict this);
Determining what actions may be taken outside of meetings, such as deciding to spend small amounts of money;
Authorizing another member to preside in the absence of the chairman;
Establishing standing committees and other roles/offices (though the various Roles are established by guideline, there's nothing saying that that list cannot be expanded, or more-formal subcommittees be formed);
Setting a quorum other than ½ of the membership;
Anything else the membership wants definitively established and difficult to change, such as establishing formal policy documents for the operations of the unit;
And, of course, prescribing a parliamentary authority for the committee.
However, it seems to me that all of these things can be done with Rules of Order and Standing Rules documents.
So here's question 2: What rules of order (if any) should unit committees establish?
The more I think about it, the more I think that maybe RONR will work fine; the committee is a board, and therefore automatically follows the small board rules (unless it gets too big, I guess). Glancing through RONR, the only thing I can see that would have to be changed is the disciplinary procedures, and that only to the extent that, similarly to how committees behave on p. 501, ll 14-26, the board could not expel a member, but only report misbehavior to the chartered organization. Even the Officers chapter would not have to be changed, I think, as everything relevant in that chapter is dictated by the bylaws. Somehow making clear in the rules of order that the committee should use the small board rules would be good, but I'm not quite sure how to do that, since it wouldn't need to be dictated, just explained.
I mean, most of what's in RONR would never be used, and most motions would be by unanimous consent or quick, fairly informal vote (perhaps with assumed motions), but that's true of any small assembly.
Sorry if this is way too long; I can shorten and break it up if it's too involved to easily respond to.