Hello !
Maybe some of you have heard about Flight sim voices US Flight crew vol.1 .. and visiting their forum I read the maker's topic about how to enhance the voice recordings for RCv4.
http://www.flightsimvoices.com/forumsm/index.php?topic=18.0
He's explaining his own technique to reduce the most possible the robotic feeling when you listen to RCv4 controllers or pilots.
First I understood that there's no magical solution because one number recorded alone will never sound smooth played in different part of a sentence because of the tones and rythm one puts in the surroiunding words.
He explains it better than me but read this : "AA42, you're cleared for taxi to runway 20L", the "2" number is always the same WAV file, but this sentence pronounced in one shot and cut in different WAV files will produce different "2" sounds.
At that point, you get there's no perfect solution but if you record a full sentence, and cut the words, instead of recording them one by one, then it may sound better than the original recordings brought by RCv4.
It sounds to me like a nice idea to introduce during development process, maybe for an enhancement in a future release.