There is a Dial-By-Name feature already in the RC platform, just not a Dial-By-Extension, an extra selectable option in the IVR settings would be ideal rather than just 'First Name' & 'Surname' as I struggle to demonstrate the use case in which iIcan deploy Dial-By-Name solution effectively.
NOTE: Currently RCs platform allows DTMF tones during ‘Audio while connecting’ and during the voicemail prompt.
This allows extension dialing from this point. if you correctly configure your inbound audio settings on a user's ext and you remove voicemail and point missed calls back to your IVR for that ext. you can build a rather convincing Dial-By-Extension feature in your existing account.