Welcome to GPLDL - we are still beta - please report any bugs via the contact form.
If GPLDL would introduce an API of some sort so we could download with curl or wget then writing an update plugin would be easy. Or even better, an internal repository. I would be very interested in working with this is GPLDL would like to talk some more.
I just want to point out, This will hide all messages from plugins and core that use the error class. You could potentially miss an important message. Just an FYI. I am looking for a better way to supress the message but yoast uses a really simple function. You can remove the function from the plugin file but that gets overwritten on update.