I think adding something like (or awareness of datum transformations generally) would make the tool harder to use for its intended audience. If you need the level of precision where tectonic plate movement matters, then you need professional level tools.
The worst distances you can expect are around 1.5m (comparing australia in 2001 when gps accuracy was improved to now). But that number can be hard to figure out if you don't have a tool that allows you to set the time of conversion :)
