@tristan.deratz I know we had a chat by email but wanted to add some of the ideas here for others too!
The Form UI components currently have a ‘Helper text’ designed, which would I think is the easiest way to provide in-place assistance on forms. It can include a link off to a full page of content that explains the jargon or complex concepts in detail.
From the Patterns pages:
Helper text
Use help text to provide additional context, information or as an example to complete a field input.
Do not use infield placeholder text.
So it probably should be used for explanations specifically on forms.
That said - I personally quite like this UK Gov form approach shown here (it’s their “Details” component, and often seen after the input field, but before the action). @jennifer.weiley recently mentioned it in another post.
A live example of the component in that screenshot is used in this Register to Apply for US Global Entry beta (Select ‘No’ and Continue past the first page).
Will you and the team be mocking up a few versions of your prototypes that might help test these various approaches?