MASSIVELY OFF TOPIC: The more I think about this, the more I think this would be the perfect homebrew hommage to TG fans. We got jacked late in the system's life. Air Zonk was amazing, but SAZ and Bonk 3 (including the CD) were such a let down. Just imagine a platforming Zonk game Megaman style. You could have shooting stages like Air Zonk, throw back stages in the Bonk universe, etc. It could be so, so awesome! 
I admit, I also thought of Zonk when Bonk was mentioned in this thread. Especially when you consider the different weapons you get in Air Zonk. It's like a Megaman Shmup, in a way. Zonk in a megaman platform style universe sounds decent.
So, I've been kicking around the idea of multiplayer mode some more. 1-4 player modes; 2 player co-op, 2 player competitive, 3 player competitive, 4 player competitive, 4 player as two 2player teams competitive. In competitive mode, you compete for score. More enemies come out and you don't share resources (life or weapon energy). You're given a fixed amount of lives and no continues. But you can purchase additional lives using your 'score' points (at the time of death) and rejoin right back in. At first, I thought doing a mutiplayer mode would be hard to balance the original game design, but if the focus of the goals relative to the game are fairly different - then I don't have to worry about balancing 1 player design with multiplayer design. Matter of fact, I could add additional changes to the stages and such for multiplayer mode.
4 player mode would be taxing on the sprite scanline limit ( four 32x32 sprites is half the bandwidth for the scanline and then add in bullets and enemies - ugh). I could limit the bullets to one at a time, per player. That would be 12 out of 16 cells per scanline. Or alternate the bullets between two frames (some games do this) so you can shoot two at a time. There's definitely gonna be some flicker though in some instances.
