Frame as ground

I'm upgrading my robot body and am wondering if there is a downside to this approach. The body/frame will be one of those 2.5 gallon popcorn tins. I'm thinking of using the tin itself as the ground. There will be 9 or so different devices connected to ground and this would make those connections much more convenient, only having to run data and power. I typically duct tape the backs of my circuit boards to cover exposed traces and they will be mounted on a sheet of expanded PVC.
Any down side I'm not thinking of?

Yes you can have the chassis as ground, but analog sensors will need their own separate ground lead which
is not connected to the chassis, just to the Arduino ground direct, otherwise you’ll inject noise directly into all
these sensors from the chassis. If there are big currents (say for motors) flowing in the chassis then all digital
devices will have to be pulled clear of the chassis too to keep voltage spikes off them.

All very high speed logic data signals should be sent as twisted-pair with their own separate ground wire
anyway, note, for signal integrity - things like SPI in particular.

So, yes, you can do this, but there are caveats.

What is the difference between this and a common ground terminal strip?

What is the difference between this and a common ground terminal strip?

The size of the antenna! The can makes a very large antenna that picks up a lot of noise from various sources. A terminal strip, not so much.