Sounds like it would be fine to just toss everything to ground early and often: screws or gaskets to chassis GND, pours around connectors for their shields, and gaskets around the connectors themselves if applicable (chassis to connector grounding). BS termination would then be to the same GND, which will be right near the connector and its shield, no problem.
Isolation and small capacitors and such, really only matters when there's, well, isolation required, or enough other stuff going on inside the box that it could interfere with itself.
For isolation, take for example if you added an isolated RS-485 port. There will be a DC-DC converter, logic isolators, and transciever (and maybe filtering and other associated EMC protection, but that's not important here, that's with respect to the interface chip). You might have the situation that, although the isolation capacitance is small (10s of pF?), it resonates quite strongly with the attached cable, which, maybe it's hard-grounded at the far end so acts as an inductor against your isolation capacitance. Given a source of internal interference (maybe a low impedance source at the grounded end, like a ground loop including a switching converter?), it could radiate quite strongly, or conversely, receive external interference could develop quite a large AC voltage across the isolation gap, corrupting data (exceeding isolators' dV/dt rating).
In that case, it might be desirable to introduce loss to that capacitance: a small capacitor (100s pF?) with significant ESR (as from a ferrite bead or resistor -- in either case, 10s-100s of ohms resistance at radio frequencies), acts in parallel with the isolation capacitance, in turn acting as a termination for the energy on the cable/shield. Instead of resonating strongly (standing waves), the cable develops much less gain. Note you're not filtering out the noise here, you're just knocking down the peaks due to a poorly damped element in the system.
It would do equally well to place a ferrite bead near the low-impedance (grounded) end of that cable, both terminating its CM impedance, and increasing the ground impedance so that less current can flow on it in the first place (and thus, less voltage develops at the 1/4λ points away from that node, etc.). Perhaps for some reason, you can't ensure a ferrite bead there: then the R+C across the isolation serves a similar purpose.
The other case, with "other stuff going on inside the box", would be more like the motherboard and expansion cards of a PC. Here, while grounding may be generally okay, there's just so much stuff going on, on both sides of all PCBs inside there, there can be some noise generated -- you've got the logic levels (or whatever), maybe it's on the order of a volt of noise, but it's also over a broad spectrum (100s of MHz to 10s of GHz). That's a whole lot less to deal with than the wild outside world -- it's not some 3, 10 or more V/m of radiated fields, or ESD or EFT. But you still need to be careful that, say you're designing an expansion card, and it has this kind of CM noise coupled through it, that noise isn't transmitted through the slot guard and connectors. So you might isolate the main PCB area away from the slot and connector area, and use common mode chokes to carry signals over to the connectors.
Since your project apparently doesn't have much inside it, it seems the latter case wouldn't really apply, and common mode currents/voltages will be easily resolved, so that little comes out from the connectors. Just a solid ground plane on the PCB should suffice.