Thank you for both your replies. It has been making me feel more confident again about doing this (although I am still not fully there!).

I have now made some modifications to my parts list:
http://www.thecustomsabershop.com/Vi...6-715379ec7fd2

Now, I understand that I can wire up the two green LEDs to one resister and then to the NBv4. As for the white LED, that can have its own resister but will only be activated anyway by the "flash on clash" feature if I wire it up that way. So, I am also wondering whether the speaker needs a resister or whether I need any more electronic components for this to work safely.

I decided to stick with the removable battery concept (obviously still using a 3.7V li-ion battery) as I quite like the idea of taking it apart (at least a little) when it needs more power. I will need to get a li-ion battery over here as they will not ship those internationally, which is another reason for keeping this as a separate piece.

I apologise if I have misunderstood anything you have said but I feel I am making some progress here.