Maybe but isnt the purpose of wire spokes to absorb impact and make the entire wheel structure slightly flexible? Anything cast is going to be brittle as and will crack at the first decent whack. (which of course creates a real problem with tubeless tyres)
I had to take my fz6n (stock running gear) on a fire trail after it had been raining. In short i would not recommend it to anyone. Was a VERY hairy ride. Managed to keep her upright, but only just. Also the suspension will mean your spine will be in need of realigning before the day is out. Dry gravel roads would be as far as i take mine again...
If the wire spokes are properly tensioned, there is no slack in them to absorb shock and deflect as you describe. The opposing spokes are supposed to be torqued to the same tension, all the way around. Should be every bit as 'stiff' as a well made cast rim...... except for the part where you have 70 or more individual parts flying in close formation compared to one solid piece. I like cast because they don't have all those holes in them, and there is no need for routine maintenance. Easier to clean, too.
I guess our definitions of decent whack are somewhat different. You could take an 8lb sledgehammer, and swing it for all it's worth and whack your front tire/wheel (like you were riding over a pot hole, or rock in the road) and it wouldn't faze the rim at all. You'd be
amazed at how big a hit a rim can take. They only bend (for the most part) when they get hit at an angle. Or when you hit something so big so fast, that the suspension cannot allow the wheel to move away at all. A Curb, at 60 MPH when you are grabbing the brakes hard, for instance. If you know you're hit something as tall as a curb, at speed, it's far better to romp on the gas and lighten the front wheel.... the back rim is even tougher.
As an example, a good friend of mine was forced off the road riding her FZ1 last summer. Riding on the highway through a construction zone, the lady driving her SUV beside her swerved to avoid a plastic trash can laying in her lane. Forced my friend off the road to the right, and she dropped the bike at 65 MPH on the shoulder. (she'd ridden motocross for years, and graduated MSF, etc. Knowledgeable rider-- lousy situation. She ended up being the 'gutter ball' at the bowling lane....) The bike tumbelled and slid on the shoulder, then turned and ran into the center divider wall at ~60 MPH. A VERY large whack. After she healed for a week or so, I went with her to assess the bike in the wrecker's yard. Fork tubes were bent, the steering stops were snapped off the lower tripple tree, there were dents in the frame from the tubes hitting.... the back swing arm had become twisted in the process so the rear wheel had about a 15 degree slant from vertical to it. And it was a hit and run, to boot.
The front rim had a scrape from the pavement on it. Still round, still true.
Living on a gravel road, and having to traverse 3/4 of a mile of gravel with a soupy layer of clay based mud on top of it to bet to pavemet has forced me to come to terms with the FZ6's capability for essentially fire road type riding.
Street tires will let the whole bike squirm around. A lot. the trick is to loosen your girp, and not lean the bike. Hang off, and let your CG steer the bike around corners. done that way, I can comfortably ride on that slimy surface up to about 25 MPH. It does tend to toss muck onto the hugger, and the fork tubes look terible afterwards..... the back rim is constantly muddy or dusty depending on the season.
I've ridden street bikes thorugh potholes deep enough to 'bottom' the suspension.... it's tougher on the suspension than it is on the wheels and tires.
