That being said a BB can only help.
^^ That.
Just because one _can_ get away with something doesn't mean it's the best decision to make. I've heard of experiences where people skipped a battery box, ran mic in, and got burned on their capture (even though they'd be previously fine). That _ONE_ special show you're at could be deemed a wasted effort because of not wanting to carry a $30 battery box. It doesn't add much bulk to the M10 and can be easily brought with. I remember the days of the WMD-D3 or TCD-D7 with a Core-Sound Battery Box (never mind mics). The M10, Ugly Battery Box (or preamp for that matter) and CA-14's/CA-11's/AT-853's/AT-943's/DPA 4061/B3 microphones are a breeze comparitively.