I wonder if some kind of "shaper" is possible without looking rediculous? And a lot of guys have big pecs, often without huge arms just some muscle on the arms.
Me, I'm not gonna give up my bench press, and I don't like wearing stuff that hurts! I'll stick to my sports bras or the Speedo swimsuit top I have now, and I may just go to woven as opposed to knit shirts or something.
Swimsuits designed for performance instead of looks tend to flatten quite well keep that in mind. A one-piecer made for speed could work very well as long as you don't mind the hassles involved like having to take your shirt off and it down to have a good old sit down bathroom visit, and the pinching in the crotch.