Male and female models - can I keep them as the same object somehow?

So I’m modeling male and female characters for a game and while the proportions are different, for the most part the geometry is the same. The only exception is the chest, with the breasts being modeled differently than the male pectoral muscles.

The only way I know how to make the chest area different is to make the female model a completely separate object, but then when I have to make changes to the UV mapping or bone weights (which I want to keep the same on each) I have to either change it on both models (hard to get exact) or scrap the female model and reshape the male model into the female and redo the breasts again.

Is there any way I can keep both models as the same object? The female could mostly be done as a shape key if not for the breasts. Or maybe there’s some way I could share the UV mapping and bone weights between models?

If this isn’t possible to do, could someone suggest a better workflow so I don’t end up redoing so much work whenever I have to go back and adjust something?