The TTS model is trained on two things: speech samples and their transcript. If you add enough sniffle-symbols every time a sniffle appears in the speech, I am confident the model would pick up on that. And then you would be able to replicate a sniffle in the generation part. The more time-consuming bit would be to add in the training data for the language model those sniffle-symbols, so that they would be organically added in the text in the text-generation phase.
But seriously, it's not worth it. I think he's a brilliant man with an idiosyncratic speech, let's leave it to that.
