Using multi-node tree picker with per-language start node id

Hello,

I have these 2 sets of categories in my site, they are part of my content tree:

- Site
- EN
- Category set ABC
- Category A
- Category B
- Category set XYZ
- Category X
- Category Y
- FR
- Category set ABC
- Category A
- Category B
- Category set XYZ
- Category X
- Category Y

I'm trying to create there "Project" documents types that allows the user to select [0...*] of these categories in two seperate fields. So I thought I would create a Multi-Node Tree Picker (MNTP), but then when I was about to set the "Start node Id" I realised that my FR projects need the FR categories and the EN projects need the EN categories.

So other than using inherited document types, is there another smart way I could do this?

Thanks!