seeking tips for transcribing a modernist score

[Justin Glenn Smith]

As a personal exercise I am attempting to reproduce a printed score from an 
ex-teacher. I have encountered a few difficulties for which I would appreciate 
suggestions.

Notes have an explicit accidental even for natural (similar to the dodecaphonic 
accidentals style), but only for their first use in each measure (this is 
actually a style I have seen in other places too, for example a Xenakis String 
quartet I was studying). I looked at the scheme code for defining accidental 
styles (I have programmed in scheme before), but I figured I would ask here for 
tips or on the off chance someone has already defined this before attempting to 
define a new accidental style. Of course I can continue using ! to force 
naturals as appropriate, so this is a low priority issue (more an annoyance in 
a large score than anything else).

I am having problems with a single measure in 8/6 time. Lilypond complains that it is a 
strange time signature (which it indeed is), and I cannot get a bar check to work 
properly (I am doing bar checks for every measure and bar number checks for each numbered 
bar to help make sure I am following the written score). In other cases where the bar 
check did not work (where a "whole note" rest meant a whole measure regardless 
of measure length, or a measure had a missing beat) I would use s (invisible notes) in 
order to duplicate the appearance of the original score (never sure whether the issue was 
an error or an idiom /experiment of some sort that is unfamiliar to me). Is there a way 
to do 8/6 without nesting it in \cadenzaOn and \cadenzaOff commands?

Relatedly, there is a rest notated as a half rest with the number 5 above it and the 
number 6 below it, which seems from context does indeed seem to be a rest of 5 "6th 
notes" - I am assuming I just need to directly tell lilypond to display the symbols 
using markup commands and use either candenza or s invisible notes to make the measure 
work? If I had written the score I would have just done a tempo change (which seems much 
more sane), but I am attempting to recreate an existing document.