A great discussion.
I would question whether there is a practical difference between bylaws and various "Guides". I believe that in treating Scouts and families fairly, either would be as binding and should be equally hard to amend, exactly to the extent that the chartered organization is willing, toe review and enforce them.
Several agreements might be necessary. Bylaws might best be reserved for spelling out hard and fast rules for Adult interaction, and interaction with the Charter Organization, and created as an agreement between Committee and its Charter partner. Guides are published to parents and is the agreement between families and the Unit, represented by the Committee, for the interaction between Scouts, families and the Unit.
Generally, I'd recommend keeping both simple, specifically prefaced with a statement that if BSA policies are found to conflict with the guidance, or are changed such that there is a conflict, BSA policy controls. There are several areas where Units and Scoutmasters are specifically given authority to make a judgment. For example:
Determining what qualifies as service hours, and how to credit the service - that is, whether a Scouts service can count for multiple purposes: JTE hours, Eagle hours, rank advancement, Awards, or other (Church, School, Order of the Arrow, etc). Rather than leave that issue open and arbitrary, the committee and the Scoutmaster should work out a consistent guideline and publish it to Scouts and parents.
Financial reporting, auditing, and signature authority.
Identifying the Committee responsibilities for Eagle Project review.
Determining the conditions and process for removing an Adult from a volunteer position, particularly service as SM or CC.
Determining the conditions and process for youth replacing a youth leader, say, a "no show" SPL or PL.
Defining an "active" Scout
and so on. There are a number of areas where guidelines are needed, or should specifically be identified as the personal discretion of the SM. Some of the issues mentioned in the discussion seem less like a matter for either bylaws or guides, but simple public announcement: meeting times, meeting places, dues, etc. should be a matter for discussion and revision based on circumstance. A simple public announcement should be more than adequate.