I've been searching for something like this for a long time: collections, text, bookmarks and the possibility of self hosting the data. This will be like a personal wiki/knowledge base! Looking forward to trying it :)

Awesome landing page too, love the colors!

Reading the comments, there is a foreignSymbols key in one of the json documents. We could be getting shared symbols soon!

A few years ago I made a template based on Mailchimp's that we still use, but it hasn't been updated in years and there are other options nowadays.

Recently I've been looking at some semi-automated solutions that use custom code to build the table layouts for you: Foundation for Emails and MJML made by the guys at MailJet.

I still haven't used any of those for any real email work, but I want to give MJML a try. It takes care of adding conditional html comments targeting Outlook and it even makes responsive email possible on Gmail's official app (although that will not be a problem anymore since Google recently announced media queries support for Gmail).

I recommend you check both of them out, see how their code works and use the one that best fits your needs :)