B2B Portal - Site Maintenance Notification to external customers

Currently, if there is any maintenance working being carried out by Cin7 on external facing web-sites, B2B Portal, and our customers try to access the site, the browser they are using just hangs, with no message/reason as to why they cannot gain access to the site. 

Can Cin7 not display a temporary banner informing external customer that the site is unavailable due to maintenance work and an estimate of when it will available?

It is not a good customer experience and gives rise to numerous, unnecessary support calls asking us why they cannot gain access.