Rigging suspended parts for animation?

I’m new to rigging/animating so this may be an obvious one but I’m designing a custom character out of custom meshes and I’m wondering if it’s possible to have some parts not touching each other (suspended in the air) while still being able to rig it for animation using attachments or just simply using the animation editor, or even for r15.

Also, if everything’s rigged properly, is it possible for r15 animations to work well with any proportion of mesh scaling (i.e shorter lower arms/taller upper arms) given that you place the attachments properly or is r15 set for the default r15 mesh scaling?