In doing this childminders would have something else to strive for and it would keep the cost of inspections down. The result would be that all inspections would be conducted on a risk assessed basis instead of the arbitrary 3 year rule that currently applies to everyone.
Instead of inspecting every childminder at least every 3 years, why not tailor when the next inspection should be due based on the latest inspection outcome. So when a child minder gets an "Outstanding" or "Good" they get inspected every 4 or 5 years: for those gaining a "Satisfactory" they are inspected as now – every three years; and anyone else gets an annual inspection.
Similarly where a childminder thinks they have improved they could then request an earlier inspection to possibly raise their outcome grading.
Other ad hoc inspections where a complaint has been made etc would of course continue.