Phase one: Typography, UI Components, Layout.
Typography
H2
Body
I like the added legibility of the two story "a"s and "g"s and the "l" with a foot. This "l" might feel a little cluttered for the reader for long passages of text. But I'm expecting that the longest read would only be four or five paragraphs. The differentiation of the letterforms will provide clarity to the informational content which will be the bulk of what is offered. I considered Source Sans, which has a lot of the same features. But decided the voice of Work Sans more closely matched Black Plum's. I am a big fan of IBM Plex. But it would be an added concern, at the very least, to have to think about every layout and component with an eye toward avoiding looking like an IBM production.
4pt grid
1rem = 16
H1 : 48/60
H2 : 36/48
H3 : 28/42
Amazingly few discotheques provide jukeboxes
Body : 16/28
Cwm fjord bank glyphs vext quizsmall : 12/18
Amazingly few discotheques provide jukeboxes
eyebrow : 12/28
Cwm fjord bank glyphs vext quiz
super_title : 68/68