Flamethrower is useful in several other situations, too (e.g. defending the bank on Goldrush). It doesn’t take much practice before you don’t fry your teammates much. When there are medics around, it can be useful in even wide open areas, such as fighting over the bridge-building point on Fueldump.
Anyhow, I’d support moving the smg to weapon bank 2, although I’ve no idea how easy or difficult it would be.

