While not directly addressing this feature request, there’s some good news for anyone seeking to ensure they don’t incur any charges.
Netlify have released a new guaranteed ‘Free’ plan, where instead of being charged overages your site is suspended, (for the remainder of the calendar month), once any monthly limits are exhausted.
It’s effectively a ‘Starter’ plan without the risk of overages.
The forum announcement is here:
The blog announcement is here:
The various monthly limits can be viewed on the pricing page: