I've posted this in another thread, and this isn't exactly an addon request as much as it is a fundamental game mechanic request, but I'd like to see script/server defineable and controllable chat and voip.
As ACRE has proven having a robust moddable communication system adds a whole new depth of gameplay, experience and immersion to ARMA and I'd like to see this continued. Below are a list of features that I would like to see in regards to communication:
Dynamically definable channels, with definable name, style (colour), VOIP quality.
Dynamically definable channel joining/leaving, either script or user controlled.
Redesigned communication UI to account for these changes, along with the ability to overwrite that UI with a custom one
I think extending the game in this direction to allow for scripters and modders to integrate ACRE features into their maps without having to rely on third party applications and plugins would be a considerable achievement.