Indeed as far as I can understand, there was a reform to standardize it which was signed by Portugal, Brazil, Cap-Verde, Sao Tomé-et-Principe, Timor oriental and Guinée-Bissau. It unified mainly the PT and BR version (to be official language at UN).
So I propose to wait for issue7863 which will rename pt_BR into pt, then we will create pt_AO which will derivate from pt. (Maybe later we create pt_MZ).
Yes, it definitely make sense to share terms with pt_Br under a general pt language, since the languages are the same, with some changes.
Currently the problem with Portuguese is in the way some words are written. Portugal decided, years ago, to change the way some words are written. So they started writing the same way Brazilian Portuguese is written. The problem is that, all African Portuguese speaking countries, none of them apply these changes. Now, we (Angolan people) still write the 'old' Portuguese, while Portugal started writing as Brazilians now write. Yeah, I know, it's a mess lol.
What I propose it's a way to differentiate between Brazilian Portuguese (pt_Br), which is already a tryton feature, and Angolan Portuguese. Just to give you a simple example: the translation for Invoice, in Angolan Portuguese we write it as Factura, while in Brazilian and Portuguese from Portugal they write it as Fatura, without the c before the t; FACTURA vs FATURA. This is just an example, there are lots of this examples that I'd like to address with the Angolan translation.