*NOTE: I'm not the guy making this game*
My player engine based on Trevor is nearing completion. I'm probably going about it completely differently than this guy, though.
As for doing swinging, just mess around with Bionic Commando. Study the mechanics and sprites and then take it from there. That game had one of the best swinging mechanics to date and it was an NES game!
And I just want to add to the issue about 8-bit games rather than 16-bit or 32-bit games. Personally, I hate 16-bit and 32-bit fan games. Sure, they look nice, but they feel more dated than 8-bit games. I mean, all you see nowadays are 16-bit or 32-bit games whenever you play video games, so there's no novelty in a fan game of that bit depth. I enjoyed SNES and Playstation games when I was in college, but now I play mostly NES games because new games just don't feel fun to me.