The official distribution of phpBB is made in available English (World English using the definitions from the Cambridge English Language Learners Dictionary). It is from this that we expect that all modification will be distributed in the same style of English. Because the distribution is only in English, and it expected of all installs to have English present, all primary MODX files for a template, or the MOD will contain edits to the English language. While the Language can be disabled, we expect it to not be removed.
On the other hand phpBB ships with two styles, one of which is installed by default.
prosilver - installed by default
subsilver2 - not installed by default but distributed with
This Leads to the MOD Team requirements that the development team have asked us to keep. First trick is to not bundle the language requirements with the template requirements. They are different requirements, so the mind set that they can be handled the same must be chucked out the window. It may be harder for those comming from phpBB2 like myself to remember these requirements.
In the main MODX file you must include the English language edits, they must not be separated, they must be included.
install.xml - contains English edits only
However you must not include prosilver, subsilver2, or indeed any template changes in this main MODX file.
/templates/prosilver.xml - contains prosilver edits only.
/templates/subsilver2.xml - contains subsilver2 edits only.
Now this gets a little more interesting, but exactly the same for image sets. In the template specific MODX file you must include the English language edits, they must not be separated, they must be included.
/templates/prosilver.xml - contains prosilver edits, and English prosilver image set edits only.
/templates/prosilver.xml - contains subsilver2 edits, and English subsilver2 image set edits only.
Now you come to localise phpBB3 modifications by applying the same principle to each of these.
For the main language system itself (anything language related that isn't an image set), you place in the languages directory.
/languages/nl.xml - contains language file edits for the dutch language.
But when it comes to localising an image set, you have to localise the template edits. This is achieved by having another MODX file for that scenario.
/templates/prosilver/nl.xml - contains prosilver image set edits for the dutch language.
/tempates/subsillver2/nl.xml - contains prosilver image set edits for the dutch language.
What this adds up to is a minimum and maximum amount of edits based on what you change in phpBB3.
The minimum is 1 MODX file for modifications that do not change templates or image sets.
The most likely case is 2 MODX files, one for code changes and English language, and template changes.
It is also 2 MODX files for modifications that do not change templates but add a LOTE (for all intensive purposes en-us is a LOTE).
It is then 3 MODX files for modifications that change templates and a LOTE, discounting image sets.
It is then 4 MODX files for modifications that change templates, and a LOTE, including image sets.
That way the user and EasyMOD only install what they need, and they can see from the directory structure what they will need. Of course it will be even more if you have multiple LOTEs and templates, and then a combination. But it tends to get complex no-matter how much sugar you add to the spoon of medicine.
I hope that addresses your concerns. As for the specification, it is now complete and you can do everything and it will not be changing.
The phpBB Modifications Team