Under file it should have "Write offline transaction" and "Put offline transaction online" or something along those words. Already has sign/verify message, sweet feature.
bitcoin-core is 99% about protecting the network by decentralising the blockchain.. so features will be a secondary thing.
much like banks SWIFT network has nothing to do with Visa's contactless NFC features.
but if you want the feature added to bitcoin-core, there is nothing stopping you talking to the dev team.. as im pretty sure that comments on this forum dont really register on the dev teams radar as a place to get feature requests..
plus because it's not really essential to the security of the network, maybe a donation to pay for their time would sway them to divert resources away from security and onto user-friendly.