This looks pretty nice! Played around with it a bit on a few templates I had saved locally—I know you're not saying here that you support emails as well, but there is at least partial support (it seems to have issues with global color variables there.)
From a development point of view I'd be a little more interested in capturing module/editable area issues than having the ability to alter input values, especially when converting items from non-Marketo setups to Marketo.
Yeah, I debated on building that into but considering the tool is mainly meant for developers, I figured it would be just as simple for them to edit it in the HTML file.
If Marketo wanted to throw some money at this. I would absolutely build all of the template features and behaviors for email and landing pages into the extension in order to develop out side of Marketo.
I just found this! After more than 3 years developing locally all my Marketo assets finally I see some light at the end of the tunnel! I wish Marketo was way more dev. friendly and it's a bit of a shame that such a useful tool is coming from outside Marketo but at least it's there.
A trillion thanks again! I'm still waiting for the day uploading HTML and CSS to marketo will be available through GIT (dreaming is free).