VHF in text format
You didn't say what radios you had or whether they were fixed or handheld.
We have nothing but Standard Horizon, 1 fixed mount at the lower helm with a RAM up to the bridge and 2 handhelds we carry while underway moving around the boat.
I've never seen a speech to text availability but that doesn't mean there isn't 1 out there.
I wear hearing aids and I have Bluetooth in the aids, it would be nice if there was a connection there, but again, there doesn't seem to be. I'll check SH further and if I find out that there is the ability to connect to aids, I'll repost.
SH does have, for their handhelds, a SSM-14A which is a submersible speaker/microphone that plugs into the radio, I'm getting 1, which would work better than an external speaker alone. See it here (file:///C:/Users/cwill/AppData/Local/Temp/MicrosoftEdgeDownloads/31a75d47-6d28-47f1-a040-4bc0d009fe2c/HX890_Brochure%20for%20Web.pdf).
I think that would be your best approach. A setup like you see the cops, have all contained.
SH make a great product AND they have great support if needed for questions.
Any specific questions PM me.
Good luck.