EDDI can read out player sent messages.
DING DING DING and we have a winner!
IMHO this is by far the best way to accomplish that and with the wealth of things that EDDI adds it really is a fantastic tool. I play in VR and as such I don't notice comms text very easily nor can I read messages if I'm streaming on Twitch. EDDI solves the first and I use another simple TTS app for Twitch called Anna. It logs into your Twitch channel via IRC and reads everything via TTS.
Finally if you're willing to throw some money at the issue have a look at the Inova voices. They are professional level text to speech voices, I bought and use Emma ($45 so not cheap). It is rather amazing how good the voices are, Emma is a British female and most of the time I can't tell it's not a human voice, it's that good.
Definitely give EDDI a go, best of all it's free. Oh but you might want to look at the tab that shows all the various things it can say to you - and turn some of them off. For example when you turn in a mission it reads the details. If you're doing something like stacking missions it can get VERY annoying as it takes longer to read the details than turn in the mission. You don't have to wait but it builds up and just won't shut up. I only use a handful of things with my favorite being the system data it reads to you as you jump from system to system. That alone is worth setting it up to me.