Enlarging the snakes might be a good move, definitely.
Just for those whose vision isnt very good. Tiny bullets do have that issue. Making them bigger would definitely help with that.
There's also the issue of the game's glaring backgrounds in later stages (which can make any bullets harder to see, particularly the tiny ones)... we REALLY need to do something about that, by the way. On my own copy of the game (well, my development version anyway) I actually took those image files out of the game entirely. They just make it way too hard to see what's going on in later levels. That's just in my copy though. However in the public version, I *did* remove all of the windows from Terminus's room, because that complaint from people kept repeating, since that fight is much harder than normal rooms.
Sorry, that's a bit of a tangent and a side issue, but this reminded me of it.