To be able to select SegWit addresses on the offline machine, you have to run the proper cli args. Look at the changelog for that:
https://github.com/goatpig/BitcoinArmory/blob/testing/changelog.txt#L14The change selector will not pick a nested SW return address if there isn't at least one SW input in the tx. This is because SW was deployed as soft fork, therefor an opt-in feature. The implementation of SW in Armory intents to respect that disposition. Think of it this way: the software will not lead to coins in opt-in/new script types without some guarantee that there was deliberate user intent.