you should head over to the forums.mtbr.com website where you can get current owners to offer suggestions (there is a cannondale specific section and a very extensive thread solely devoted to the Bad Boy).
Off the top of my head you are likely looking to go to a 26" wheel if you want tires with cush larger than 38c (presuming you have the lefty solo fork), and even then for clearance issues you likely wont go larger than a 2.2" tire. (maxxis hookworms 2.5; schwalbe Big Apples 2.0, 2.15, 2.35; Kenda Kiniptions 2.3, etc). For sand these are still not ideal, frankly nothing beats a snow bike if you are riding on sand so we are talking Surly pugsley (moonlander, etc). The bad boy is not an ideal match for this kind of riding, at best it can be made into a very good XC mountainbike, not a sand bike, that is just not it's forte and the biggest tires you can shoehorn onto it's frame/fork are still not ideal for this.. Might do in a pinch not def not an ideal match at all, likely more chore than joy at best.
Platform pedals...well there are scores of great pedals, look for DH type pedals if you want the most outright strength. My bikes have a combination of Truvativ Holzfeller DH, CrankBros 50/50, Azonic 420, etc, etc, etc..hordes of good pedals out there. I have Xpedo curves on mine, they suit the bike and the riding I do but they are biased on weight saving not strength so not ideal to subject to rock bashing else they are very nice. Good wide platform and pins with decent balance between grip and comfort. Not the most aggessive pins but grip well enough for my street riding.
Carbon fiber handlebars...the world is your oyster... Easton Havoc, Truvativ Noir, Crank Bros Iodine just to name few assuming you were looking for Mountain biking carbon bars..