[WIP, DNM] Foundation cross-import overlay

[grynspan]

[One line description of your change]

Motivation:

[Explain here the context, and why you're making that change. What is the problem you're trying to solve.]

Modifications:

[Describe the modifications you've done.]

Result:

[After your change, what will change.]

Checklist:

• Code and documentation should follow the style of the Style Guide.
• If public symbols are renamed or modified, DocC references should be updated.