In CC 2014, Flash allows you to create a "custom" brush of a slanted circle or square. A start, but I also need to use brushes with jagged or softer edges. If I could create a brush out of a vector image I've painted, then I could do more with the brush tool and create better artwork. Then users could share their unique brushes in an online community, all similar to Photoshop's already familiar/powerful brush workflow.
The custom brush tool does not currently allow creating a brush from a vector image. This document explains how you can use the custom brush tool functionality:
It's just a suggestion! It doesn't seem like an unreasonable request for later down the CC release line.