Thanks @bernhard for your message.
I'm in the middle.
Functionalities is very basic, journalists can choose a name, create/edit/delete their articles, reply to comments... done.PW backend UI is good to admin but could be better for my users ( in fact they are majority of 65+, display only personal entries, "bigger" articles list with thumbnail,...)
If building a dedicated template is possible for PW admin to have a custom UI and match look and feel, I think it would be my choice. Users are kind of "trusted" (account are created manually by admins).
If not, I'll do the other way and search a way to connect a tinyMCE textarea with a images field like in the PW admin to have helper and security functions