Re base template--I want to just double verify that this base template is 7.0, not 7.1? UPDATE: it appears to be 7.1, but does it have some unique develop mode-esque features re being able to see all the templates? This would be helpful to understand re below use case.
Also, in what circumstances would you want to start with the base template (7.1?) vs with Brine, for those who probably need developer mode / 7.0?
Use case: I'm hoping to add about 1000 lines of someone elses custom CSS into Squarespace (and somehow massaged to work with Squarespace, if possible--is this what developer mode is for?) in order to implement a workflow that lets me type offline in Markdown, and pre-convert (with a Pandoc filter) to HTML that will then, when pasted into Squarespace, display sidenotes in margin. Mentioning this in case it affects your answer to the 'base theme vs Brine' question in my case.
(Here's the CSS theme that will render sidenotes in my converted HTML. The developer who wrote it worked on Dropbox paper, so I think it's probably well-crafted? https://github.com/jez/pandoc-markdown-css-theme/blob/master/public/css/theme.css Example styling demo, here: https://jez.io/pandoc-markdown-css-theme/#usage)
If I can add this system of formatting to Squarespace, at least when desired (definitely in blog) I'll be very happy, but not really clear on if and how it can be done, at this stage. I have a front-end guy helping me, but this is a very specific, kinda odd project, I think?