Here is a recent picture of my BITX40v3. I have added a top and sides to the plastic case, the top and sides hinge up as a single unit out of the way so I can access the circuit boards easier.
The unit on top is a Radio Shack Realistic DSP-40 which greatly improves the receiver audio. Also shown are a 3D printed straight key and paddles. The black button beside the tuning knob is the fine tune which allows me to use one hand for tuning (hold the button in with my thumb while turning the knob with my fingers - gives 1 Hz tuning resolution). Using a 10-turn pot is a must.
I have added a stereo jack to the "microphone" box and now use a coiled stereo patch cord I found at a Dollarama.
I will still need to figure out where to install the two CW touch-paddles on the front panel for the latest sketch (v1.26 at this time). I also need to add an audio AGC circuit yet, although the DSP-40 does help somewhat.
One thing I have found is that its important to make the removal of the circuit board easy, as its always coming out for more mods to be soldered on. AL - VE3RRD