"No Icon" option for Callouts

I love the new callouts, but if find I’m not using them because there is no way to get rid of the icon. The available icons are okay, but sometimes there just isn’t one for what I want - and sometimes I just don’t want any icon there at all. I would love to have an option for “no icon” - just show the text I put in and collapse the space where the icon would have been.

For an element that is meant to be prominent on the page, this seems like a no-brainer to me: I don’t want to have a close-but-not-really-what-I-mean icon calling all that attention to itself.