On my Ratrike the track is fairly narrow, and I have long arms, so I am able to reach the outside of the wheels to reverse, despite having chunky wooden mudguards on.
I do like having mudguards as my first time out, on grass, I ran over some hidden dog poo with the right front wheel and got splatted in the face!
Drum brakes are a bit more fiddly to sort out, especially trying not to have an asymmetric layout as many brakes, drum and disc, don't come in left and right hand versions.
I am designing mine around having a front and rear SA drum backplate, as they are handed differently. If it doesn't work out then I might make my own and have twin leading shoes. It then becomes quite a major engineering project.