I was also a bit wondering about these new additions and why we haven't seen them in the OT.
But it makes a lot of sense I think: Every single film in the OT also added new trooper variatiants or vehicles (Snowtroopers in ESB, Scout Troopers in ROJ, etc.)
And the new things in Rogue One simply fill in the gaps. Shoretroopers obviously for beach landings etc., and the U-Wing as Rebel landing craft. The TIE striker is for aerial combat.
I don't like the U-Wing too much, so I might only get the Jyn Erso minifig. And the shuttle is too bulky for my tastes, so I'll buy Krennic separately (and get the Death Troopers in the Battle Pack).