Um, it seems like there are many bikinis that aren't, uh, Brazillian -- in other words, ones with more behind than just pieces of string and more in front than a g-string, and they are still bikinis. I see them for sale all the time in the summer, they are not esoteric items reserved only for old grannies. You are saying the stretch marks would show unless you wore actual shorts with legs? And your pubic hair would show? How high up does it come? Even in the teenage-girl shops, there are bikinis with real bottoms and normal fronts. Not all bikini bottoms are like what showgirls in Vegas wear when they are topless on top, surely you can find trendy bikinis that have behinds.
My suggestion regarding shaving is not to bother, but to trim the sides with scissors if you think the bikini front is not wide enough to corral the hair. Shaving does cause itching, and it's not worth it.