Five short sections that discuss the various publication aspects of a Lectionary. First, a note on psalms and gospel acclamations:
114. The texts for the chants are always to be adjoined to the readings, but separate books containing the chants alone are permitted. It is recommended that the texts be printed with divisions into stanzas.
This gives improvising singers the option of rendering the psalms right from the Lectionary–which would be my first choice. In my parish, I have a chopped-up hymnal I use to insert psalms into the Lectionary directly.
115. Whenever a text consists of different parts, the typography must make this structure of the text clear. It is likewise recommended that even non-poetic texts be printed with division into sense lines to assist the proclamation of the readings.
One wedding pet peeve is seeing the lectors come with densely-printed Bible texts, No wonder some read so fast. A good friend’s peeve is when the liturgist or clergy write directions into the Lectionary. A judiciously placed post-it note is quite enough. Used very sparingly.
116. Where there are longer and shorter forms of a text, they are to be printed separately, so that each can be read with ease. But if such a separation does not seem feasible, a way is to be found to ensure that each text can be proclaimed without mistakes.
117. In vernacular editions the texts are not to be printed without headings prefixed. If it seems advisable, an introductory note on the general meaning of the passage may be added to the heading. This note is to carry some distinctive symbol or is to be set in different type to show clearly that it is an optional text. 
I find these introductory notes less helpful. I always look for Lectionary editions that lack them.
118. It would be useful for every volume to have an index of the passages of the Bible, modeled on the biblical index of the present volume.  This will provide ready access to texts of the lectionaries for Mass that may be needed or helpful for specific occasions.
I do find the biblical index very useful.
Any other suggestions for Lectionary publishers?