Add more space between arbitrary groups of notes

[Svetlana]

Hello all,

I make scores where two lyrics lines share the same notes but have different 
note groupings. Here is an example.

\version "2.14.2"
melody = \relative c''
{
  \cadenzaOn
  \phrasingSlurUp
  \slurDown
  g2 (a4 \(bes!) a2\) a8 ([g] f4) g1 (\(g4. f8 e4 d\) d8 \([e] f4\) e2 \(f g1\) 
d4 \(g2\) a1 e4 \(f2\)) d1 \bar "|."
}
text = \lyricmode
{
  la -- pa -- pa la -- la
}
textI = \lyricmode
{
  la2 pa1 la2 la1 \skip1 la2 la1 \skip1 la2. pa1 pa2. la1
}
\score{
  <<
    \new Staff = mymusic <<
      \new Voice = "one" {
        \melody
      }
    >>
    \new Lyrics \lyricsto "one" \text
    \new Lyrics \with { alignAboveContext = mymusic } \lyricmode {\set 
associatedVoice = #"melody" \textI}
  >>
}

I use phrasing slurs for the upper line of lyrics to show how the notes are 
grouped for it and I have to use lyricmode and explicit lyrics duration for it.
Now I want to add some space between each note group, belonging to upper 
lyrics. I've tried to use spacer rests and add s1 between each of the groups. 
That looks better, but 
1) I must add \skip1 between each syllable, belonging to textI (upper lyrics). 
2) Sometimes spacer rest doesn't add desired amount of a space and adding 
another s1 does nothing.

I have three wishes that I can't accomplish:
1) I'd like be able to add more space between notes where s1 doesn't help.
2) I'd like to get rid of extra skips in lyrics,
3) The best I could wish - keeping the spaces, get rid of explicit syllable 
durations in upper lyrics (textI) at all.

Even first of them would be much of help.

Thank you,
Svetlana.