Welcome to the club.
First off I would like to applaud the Carbide3D team for their enthusiasm and customer service. I think everyone would agree that to build a high quality machine like this for this price is quite an accomplishment. Anyone pricing thick aluminum can see how expensive this will be.
I bought mine based on its solid plate structure with the idea of modding and eventually building my own. My goal is to cut steel and am focusing on rigidity and sound suppression.
I have thought long and hard about this and am addressing the following issues:
1) Replacing the thin composite top with 1/4" 6061 T6 aluminum and possibly the bottom with either 1/8" or 1/4" aluminum or stainless. 1/8" 304 SS cover for X axis bearing slides. These will be bolted solidly to machine frame and act as a mounting point for future mods. While the Nomad is a rigid machine especially given its low power spindle, this should improve rigidity, sound and chatter.
There are Z stepper clearance issues because of the way the stock top floats in between the bamboo sides and off of uprights. It's a very tight fit. I could probably just sand down the top of steppers, but I may make short risers out of 1/8" or 1/16" aluminum bar and add some anti-static rubber mat or thin neoprene to act as a vibration dampener and seal the air leaks. I'm leaving a 1/4" extra depth in case I want to add plate to back and keep stock plastic for a total of 1/2" of dampening.
2) Plexiglass door has slight play and doesn't seal all the way. Adding rubber U channel to all sides and adding magnets for alignment
3) Thin neoprene between frame and bamboo sides for noise suppression.
4) Design or buy some combination of vibration dampeners/leveling feet.
I like your idea of the chip tray. Maybe integrating all of these in one unit with mist coolant/vacuum?
5) If at some point a much taller and powerful VFD or BLDC spindle option becomes available, I would add taller risers and design a thick composite, fully insulated enclosure.
6) LED lighting around spindle . Haven't figured out how to power off of Arduino and route wiring cleanly.
As it is, it's an awesome machine. You can't get anything better really unless you step up to a Tormach or something. And that is basically a small industrial machine of 400 pounds.