My Rogue trader Style Campaign, PC confirmation and first "mission"

after multiple confirmations from all players one of my players will be playing a marine which i made a Home World/Background amalgamation to represent his chapter

with that we ended up with (Do note that all chars will end up with around 9k XP total)

A Dark Angel Neophyte Warrior

A Highborne Imperial Guard Rogue Trader Desperado

A Forge World Adeptus Mechanicus Tech Priest Chirurgeon

A Forge World Adeptus Mechanicus Skittari/Tech Adept Assasin

A Void Borne Navigator (doing a similar thing to Space Marine) Mystic

and for last a Hive World Arbites Seeker

Since theyre going to a system that was cut off the imperium the first planet will be a agri world that is suffering a problem with mutants and abhumans (Beast men specially)

I plan to have some leads to the main story/mistery but it will be more a standalone mission to really get the players into their characters

Any thoughts, recommendations, warnings?