Profile form error trapping

A shortcoming of the user profile form is the lack of inbuilt error trapping, so that if mandatory questions are not answered and people don’t check the whole form after clicking submit, then nothing is saved.  The best solution would be to have errors showing on field completion, rather than after attempted form submission. (Alternatively, they might be displayed in a list, as this code snippet shows – I think using the fields validation function – but seemingly only after attempted submission, which still has the risk of people leaving after hitting submit).  I’ve put big warnings in the form to not leave before checking that submission had no errors, but people still do.  This issue causes huge frustration for end users – we use the plug-in for artist submissions to our large community arts festival – so if anyone has a solution we’d be most grateful.