I would like to share my knowledge. Maybe it's helpful for someone reading this and is also crazy enough to improve lip sync for another language. ;-)
I'm talking about BioD_CitCas_530Goodbye.pcc as an example for an animcutscene which isn't editable with Face FX Editor.
1. Back up your file before doing anything!
2. Don't panic! It's not that bad. You get used to it.

Exp 455 contains files for people in background and their animation.
Exp 456 contains Kaidan's cutscene, if romanced.
Exp 457 contains cutscenes for every romanced Char and MShep.
Exp 458 contains cutscene for Joker (unromanced MShep).
Looking at Exp 457 - Exp 250 to 257. These are the files with lip sync.
250 Steve
251 Ashley
252 Jack
253 Liara
254 Miranda
255 MShep unromanced
256 MShep straight
257 MShep gay
Choose one. Go to Debugging -> Dump complete export to binary file. This is the file you want to change.

Offset F130: "54" means that following 84 hex values are animations used in this scene.
Look at this name list and you know which value belongs to which animation, like "43" for "jaw+".
Nametable.pdfThis name list is at the beginning of each FaceFXAsset file and can vary a little bit (so I create table above).
Offset F3D0: "40 96" are all animation points summed, starting with EF EE 9A 41 to BC BB E4 42 at Offset A57D0. There again is "54", because now 84 hex values are following telling you how many points belongs to each animation. Jaw+ (70th value) belongs to "74". So Jaw+ has 116 points.
Now open Face FX Editor and load a LOC version of Goodbye. Choose a char and create your desired line. Remind new time line! At least 25 seconds before first animation. Most chars have 3 lines. You have to combine all of them in one.
Example: "Back to fight" at second 27, "Oh come on now ..." at second 36 and "... It's been a good time" at second 58. It saves you time, if you rearrange animations to sequence used in FaceFXAsset file. For Goodbye it's always M, OH, ZZ, EH, Open, OW, FV, TH, N, L, G, Flap, EE, Jaw+, Jaw- (obviously for humans and asari). Save it, use Package Editor to dump it to a binary file.
Now comes the very difficult part of it. You have to copy and paste each animation to correct point in correct sequence into your other, original binary file.

This image shows parts of 3 animations from original file. First one ends at offset 9CC40. Then there's one with just 2 points - 0 and BC BB E4 42, followed by the beginning of third animation starting at offset 9CC70 with 0. This is how animcutscene files are build. I don't know why there's always this line with no points between 2 animations. It's there and you have to count it. Second animation contains 2 points, even if in game this animation doesn't play.
Face FX Editor does a lot of work for you. It counts all points. You just have to add 1 point to each animation (due to this one line with no values), calculate new amount and replace old values with new.
If animation like L doesn't have points in Face FX Editor, the original binary file still needs this 2 point in image above.
Maybe later I can try to delete a complete animation or try if it work's without this seperating line, but at the moment I'm done with it. Sorry.

Now, save your new original binary file, got to Package Editor, open Goodbye.pcc, go to EXP 254 -> Edit -> Replace with BIN - > choose edited BIN file and save your changes. Just autotoc and start game. If it crashes, you probably messed up calculating new values.
I really hope it's understandable.
I needed 10 min for my last line from FShep. But it could take much more time, if you have to create a complete new line with exporting and importing and testing for correct timing due to this copy and paste thing and converting values over and over again. But once, you have the correct animation and just have to improve timing, it's really quick.