"Ancient and modern from one source"

[C.Flothow]

Editing ancient music often implies that you have to halve note values 
to make the score readable for modern musicians.
On the other hand it is much easier to correct your score if you can use 
original values (and sometimes you want to use both versions anyway).
I've tried a number of ways to get a reasonable work flow but  I've got 
still two questions concerning the following snippet:

%  --------------------------------------

\version "2.12.2"

FileLong = {g\breve   g \time 3/1  f fis1  g\breve a1 a b c2 \tag #'MA 
{a~ \bar "'" a} \tag #'MB {a1} g1 g2 f1  \time 2/1 e\breve }

FileMedium = {\time 2/2 g1  g  \time 3/2  f fis2   g1 a2   a b c4 \tag 
#'MA {a~  a} \tag #'MB {a2} g2 g4 f2    \time 2/2 e1}

FileShort = {\time 2/4 g2 g \time 3/4 f fis4 g2 a4 a b c8 a~ a g4 g8 f4 
\time 2/4 e2}

              
\layout {
   \context {
       \Score
       \remove "Timing_translator"
       \remove "Default_bar_line_engraver"
       \remove "Time_signature_engraver"}

   \context {\Staff
       \consists "Timing_translator"
       \consists "Default_bar_line_engraver"
       \consists "Time_signature_engraver"}
}

\score{<<\new Staff        
       {\override Staff.NoteHead #'style = #'petrucci
       \override Staff.TimeSignature #'style = #'single-digit
       \override Staff.BarLine #'transparent = ##t
            \override Rest #'style = #'baroque
       \set suggestAccidentals = ##t
       \clef "petrucci-c1"
       \key g \major
       \time 2/1
       \clef "petrucci-c1"
       \scaleDurations #'(1 . 4) {\transpose c d \relative c'' 
{\keepWithTag #'MB {\FileLong }}} \once \override Staff.BarLine 
#'transparent = ##f \bar "|"}
   \new Staff
           {\override Staff.NoteHead #'style = #'petrucci
       \override Rest #'style = #'baroque
       \override Staff.TimeSignature #'style = #'numeric
       \set Staff.defaultBarType = #'"'"
       \numericTimeSignature
%        \set Staff.timeSignatureFraction = #'(2 . 2)        
       \key f \major
       \scaleDurations #'(1 . 2) {\relative c''  {\keepWithTag #'MA 
{\FileMedium }}\bar "|"}
       }
   \new Staff{
       \key f \major
       \relative c''{ \FileShort }
       }
>>}

% ----------------------------

1. Is it possible to have ONE source for the three input files? How do 
you do it?
2. In the middle staff a bar line is printed only at every other bar?  
How can I avoid that?
   If I leave the Timing_translator in the score environment every bar 
line is printed but I've found no way to have correct time signatures 
within the staff.
   What have I missed?
Thanks
Chris