Whilst the case would set a precedent, it would only apply to a limited set of very specific circumstances. In this case the offence was importuning. In the 1970s gay men would be charged with this if caught cottaging (and policeman would lay in wait to catch people), that being consensual sex between two males. They would be offered a caution (which requires an admission of guilt) and not advised of the future implications for employment. There have already been instances where such offences have been removed from records for gay men (no idea if they were trans or not).
The principle set by such a case would be very narrow, and would be about righting the wrongs done against gays by past generations. It would definitely not be a free for all for sex offenders to have serious offences wiped from their records.