My feature request to add to your pile (possibly a lonely one, since maybe it's just unique to how my brain works):
I really want a scratch pad like this to have UX that supports "inverted" order. Meaning, new blocks get added to the top of the page instead of the bottom. The blocks naturally flow in descending order of creation rather than ascending. The scratch pad always opens at the top of the page. Over time, blocks thus end up "decaying" toward the bottom, with the most relevant at the top.
It just fits better with how my brain works.
I also +1 the sentiment given elsewhere in this thread to bias toward ignoring the vast majority of these feature requests and preserve the simplicitly of what you've built. That includes mine!