I'll be using a converted keg, so I don't need to worry about that aspect.
That's actually why I'll need a HERMS coil...Little to no insulation on my mash tun.
I have a 1 rpm motor that I'll use to stir the mash (as long as it has enough torque to stir it).
I don't need a paddle, per se...Just stainless steel fingers to circulate the liquid into the grain bed.