"... is the ring a load-bearing component, thus making it unsafe to drive the car without the ring installed?"
tl;dr: Not exactly but close enough. You do need those rings and, if you lose one, you should replace it.
Over at ECS Tuning, they have a post about this exact issue. Quoting from Why You Need Hubcentric Rings for Aftermarket Wheels:
Having to open the bonnet or hood to remove / refit said fuse or relay is so* obvious and time consuming same as grovelling under the dash for a fuse or relay there. May just as well remove a coil lead or the dizzy rotor arm which was done on older cars by some.
I put a kill switch on a Volvo 240 in the row of standard switches, in fact it was also a spare ...
if you just want something quick and simple, removing the starter relay or engine computer's fuse/relay is generally enough. Just make sure to remove the ignition side fuse for pcm and not the keep alive memory fuse.
Cant imagine you would cause any damage other then maybe widening the terminals in the fuse box more then normal