Customise Access denied pages
if a user doesn't have access to a SharePointOnline Subsite or site collection it would be nice if we could customise the access denied page with our own content and branding, instead of the default Microsoft white page with a box.
I also need this option. MS asked me to post my interest so we in the user commuity can voice our request.
Also would like to customise Error Pages as well so I can insert application Insights code to track problems that users are experiencing.