I think they're different enough to say 'pick a lane'. IR and body are very complementary. A good IR needs solid body skills. Breast and IR are very different. And if you're a breast trained rad right now, you're gonna be shoe-horned into a lot of breast time cuz that market is crazy right now. Not the best thing for a fresh also-IR trained rad.
Word of caution to those looking to keep a full gamut of skills: it's great for the group but it can really drive your schedule in a way you don't want. If you're IR/breast trained you're gonna get a ton of breast time...... when you probably want a lot of IR time fresh out of training to solidify/build your skills.
I'm in a large group that does mostly sub-spec work. I do 90+ percent of my time in neuro. The old guys in my section don't do anything but outpatient neuro (sans procedures). I get thrown all over town covering OP neuro, OP neuro with spine procedures, hospital neuro seats and even OP general/body slots. My flexibility (to the group) hurts me, cuz i have to seats I wouldn't otherwise want to cover. Not saying that might not appeal to some people, but its something to consider.