I've never seen a brushless drill personally, and I'd think they'd be fairly rare given the motors usually have low startup torque, which is not what you need when drilling. I mean I suppose if you can take the motor out of the drill, pretty much all brushless work on the same principle, just connect three leads to your speed controller. But I have no idea how good they'd be. It's only the brushed ones that have been proven for use in Featherweights. Was there any specific problem you were having, and could we get a picture of the drill's insides to get a better idea?