Wait.
MegaMan Star Force games have post-game bosses too?
...
First thing I'll do with PC-internet is get guides for EVERY single game available here. All of them. Unless some games don't have any...

I rather like the Graveyard theme from MMBN6 though I hear there's cut content?

Well yeah, the games have bonus dungeons just like the Battle Network games. The bosses either tend to be stronger versions of the story bosses or a unique boss. Let's just say that getting all Mega Cards is one of the most difficult things in the entire game.

That's true. In the Japanese version, Graveyard has 2 parts. The first one (containing graves for all the Navis from the previous 5 games) was cut from the US version as was an area containing the Navis from Rockman.EXE 4.5. Also you could fight The Count from Boktai as a boss, which was also cut from US copies.
Then again, I've seen several hacked MMBN6 battles involving The Count, so I know that he's for real.