The UI elements have been made to fit vanilla's content mostly so it is possible you'll find these limitations when you start adding lots of stuff.
You might need to find alternative ways to provide the features you're after in your mod.
For example, it's possible to place armory interaction points which are configured to show different sets of items. You'd need to go into map modding at this point to place those interaction points around the static armories, or, create several types of mobile armory trucks where each provides different items.
In the vehicle case, the
item_container tag can take in a
soldier_group parameter. You'd add a new
soldier tag in a faction and define resources for that group, and the vehicle's armory interaction point would then show items available for that group.
In the map case, you'd probably locate an existing
item_supply (or
weapon_rack, it's an alias), and duplicate it somewhere nearby the armory mesh. In its description field you could add
soldier_group = xyz; for this point to show xyz group's items.
The radio UI is more problematic. One way that comes to mind is that you'd use hotkeys that you'd use to browse pages of calls. You'd need to have a piece of script running in the mod that would listen for a particular chat command coming from the player via a hotkey and react to it by changing the set of enabled call resources in the player's faction (
http://runningwithrifles.gamepedia.com/ ... _interface you'd register a Tracker object to listen to a chat_event and send faction_resources commands to the game). Hotkeys can be defined with hotkeys.xml (download this
http://www.runningwithrifles.com/wp/hotkeys.xml for basis and place it somewhere in your mod folder), there are key bindings in the key config menu. I know this would be quite a bit of work, but hey, at least it's possible

The obvious downside with this approach would be that the available calls for bots in the faction would change each time you change the page, but depending on the mod it might be acceptable, maybe you have no friendly bots or they don't need to use calls. Same goes for using it together with other players online.
Quite likely other possibilities exist as well.