For point4: Internalization of Email Body template – Might be good to validate from OpenMRS team (maybe post on their slack channel this question?). Having Global Properties like <attribute>.<locale>=<value>, will definitely work – but if there is an i18n framework in OpenMRS for such kind of data, that would be good to double check.
Found a related discussion, but the JIRA issue is currently marked as Won’t-Fix, due to inactivity.
cc: @grace : is there someone from OpenMRS who can confirm if there is a better way to manage translations for different email templates (not concepts).