G'day Dominique,
After a short consideration I would approach this thus:
Use a visible 2/4 + 3/8 time sigs., invisible 7/8, use normal plus broken bar lines, use a tempo staff to manage the change in metronome marks that would likely be required to maintain tempo (asuming the beats remain constant), placed between local repeats with the repeat number set to handle all the full bars
Something like this:
!NoteWorthyComposer(2.5)
|Locale|ACP:1252
|Editor|ActiveStaff:2|CaretIndex:1|CaretPos:9
|SongInfo|Title:""|Author:"<Name>"|Lyricist:""|Copyright1:"Copyright © 2012 <Name>"|Copyright2:"All Rights Reserved"
|PgSetup|StaffSize:16|Zoom:4|TitlePage:Y|JustifyVertically:Y|PrintSystemSepMark:N|ExtendLastSystem:N|DurationPadding:Y|PageNumbers:0|StaffLabels:None|BarNumbers:None|StartingBar:1
|Font|Style:StaffItalic|Typeface:"Times New Roman"|Size:10|Bold:Y|Italic:Y|CharSet:0
|Font|Style:StaffBold|Typeface:"Times New Roman"|Size:8|Bold:Y|Italic:N|CharSet:0
|Font|Style:StaffLyric|Typeface:"Times New Roman"|Size:7|Bold:N|Italic:N|CharSet:0
|Font|Style:PageTitleText|Typeface:"Times New Roman"|Size:24|Bold:Y|Italic:N|CharSet:0
|Font|Style:PageText|Typeface:"Times New Roman"|Size:12|Bold:N|Italic:N|CharSet:0
|Font|Style:PageSmallText|Typeface:"Times New Roman"|Size:8|Bold:N|Italic:N|CharSet:0
|Font|Style:User1|Typeface:"Times New Roman"|Size:16|Bold:Y|Italic:N|CharSet:0
|Font|Style:User2|Typeface:"Times New Roman"|Size:8|Bold:N|Italic:N|CharSet:0
|Font|Style:User3|Typeface:"Times New Roman"|Size:8|Bold:N|Italic:N|CharSet:0
|Font|Style:User4|Typeface:"Times New Roman"|Size:8|Bold:N|Italic:N|CharSet:0
|Font|Style:User5|Typeface:"Times New Roman"|Size:8|Bold:N|Italic:N|CharSet:0
|Font|Style:User6|Typeface:"Times New Roman"|Size:8|Bold:N|Italic:N|CharSet:0
|PgMargins|Left:1.27|Top:1.27|Right:1.27|Bottom:1.27|Mirror:N
|AddStaff|Name:"Staff"|Group:"Standard"
|StaffProperties|EndingBar:Section Close|Visible:Y|BoundaryTop:12|BoundaryBottom:12|Lines:5|Color:Default
|StaffProperties|Muted:N|Volume:127|StereoPan:64|Device:0|Channel:1
|StaffInstrument|Trans:0|DynVel:10,30,45,60,75,92,108,127
|Clef|Type:Treble
|Key|Signature:C|Tonic:C
|TimeSig|Signature:2/4
|Text|Text:"+"|Font:User1|Pos:0|Wide:Y
|TimeSig|Signature:3/8
|TimeSig|Signature:7/8|Visibility:Never
|Note|Dur:8th|Pos:-6|Opts:Stem=Up,Beam=First
|Note|Dur:8th|Pos:-5|Opts:Stem=Up,Beam=End
|Note|Dur:8th|Pos:-4|Opts:Stem=Up,Beam=First
|Note|Dur:8th|Pos:-3|Opts:Stem=Up,Beam=End
|Bar|Style:BrokenSingle
|Note|Dur:8th|Pos:-2|Opts:Stem=Up,Beam=First
|Note|Dur:8th|Pos:-1|Opts:Stem=Up,Beam
|Note|Dur:8th|Pos:0|Opts:Stem=Up,Beam=End
|Bar
|Note|Dur:8th|Pos:1|Opts:Stem=Down,Beam=First
|Note|Dur:8th|Pos:0|Opts:Stem=Down,Beam=End
|Note|Dur:8th|Pos:-1|Opts:Stem=Up,Beam=First
|Note|Dur:8th|Pos:-2|Opts:Stem=Up,Beam=End
|Bar|Style:BrokenSingle
|Note|Dur:8th|Pos:-3|Opts:Stem=Up,Beam=First
|Note|Dur:8th|Pos:-4|Opts:Stem=Up,Beam
|Note|Dur:8th|Pos:-5|Opts:Stem=Up,Beam=End
|Bar
|Note|Dur:Half|Pos:-6
|Bar|Style:BrokenSingle
|Rest|Dur:4th,Dotted
|AddStaff|Name:"Staff-1"|Group:"Standard"
|StaffProperties|EndingBar:Section Close|Visible:Y|BoundaryTop:10|BoundaryBottom:10|Lines:5|Color:Default
|StaffProperties|Muted:N|Volume:127|StereoPan:64|Device:0|Channel:2
|StaffInstrument|Trans:0|DynVel:10,30,45,60,75,92,108,127
|TimeSig|Signature:7/8
|Bar|Style:LocalRepeatOpen
|Tempo|Tempo:120|Pos:9
|Rest|Dur:8th
|Rest|Dur:8th
|Rest|Dur:8th
|Rest|Dur:8th
|Tempo|Base:Eighth|Tempo:120|Pos:9
|Rest|Dur:8th
|Rest|Dur:8th
|Rest|Dur:8th
|Bar|Style:LocalRepeatClose|Repeat:3
!NoteWorthyComposer-End
There may be better methods, but this would likely cover your needs.