Ok, the box is finished and I rode to the grocery store today to test it. It's just a couple of km for the whole trip but I had some great feelings. No more noises on any bump. Very good balance! The bike driving is definitely improved. I also feel more comfortable leaving the bike parked (and locked) outside the grocery store. I think it looks more stealth (less wires visible) and less "strange".
Anyway I am pretty happy also about the key switch! I feel like I'm riding a motorbike
Some more photos:
This is a temporary closure of the side. I am going to put a lock as soon as I figure out the best way to do it.
Lifting the panel for inspection and/or recharge.
Top view. Even with the keys inserted I can pedal without hurting my legs or touching the wood frame.
Next additions: External jst cable to connect 1-8s alarms outside the box (i am waiting for the cables/connector to arrive in my mailbox), a lock and more "reinforcement" to keep the frame into place.