2021 - Vote Here for the Game You Want!
Honestly there's not a whole lot of *substance* to the Mandos in the EU even, and I think that's where more recent additions kinda went wrong. They were a Warrior Culture that valued honor, and 'the way' or whatever you wish to call it. Or, well, are. They follow the Mandalore, provided the Mandalore has earned the right to be followed. They're a surly bunch though, and while they are a warrior culture, warriors aren't the only thing they value. Farmers, mechanics, etc, everyone has a trade - they just all also know to take up the sword if needed.
For me in particular, if we go with the Mando game, I'll be drawing on some history of the Supercommandos and their Codex for my character. Mandalore of around 60BBY was Jaster Mereel, who founded them and tried to bring back the 'old ways', which I think was where the Death Watch came into prominence? I dunno.
Either way, you're fine to get creative however you like honestly, you know what we're doing!
Oh, and I'd be on board with former clones being brought on board. There's precedence in a number of cases, so it could be fun!