A very interesting question and one that requires a serious amount of legal back and forth. I know here in the UK, there was a case where a woman (sex worker) consented to sex with a client, who then refused to pay. She attempted to have him charged with rape, as he'd gained sex under false pretences, but the High Court ruled it was 'fraud'.... I suspect stealthing will have a similar set of discussions. Consenting to one thing is not consenting to all things - so if you have been very specific about the full nature of the consent, then any deviation of that could be considered sexual assault - that's certainly where I'd want to see the law headed. It cannot mandate specifics, if someone verbally consents to sex with someone else in a wig and they take the wig off, you'd be hard pushed to argue that constituted a serious sexual assault - the interesting question is 'why not?'.