"Buried Treasure" is a good plot hook.
Lets say the players either get intel about a cache of mothballed mechs (or LosTech). Or one of their clients can't pay them in C-bills, but has the location of a cache.
Now they have to work their way towards the planet, fighting their way through enemy territory to get the gear they need to fetch the treasure.
Then they get it and get to be bosses for awhile, with all the cool toys.
And then the Clan Invasion (or whatever) hits.