Re: good idea or bad one
Your seat looks good, I second everyone on strength, etc. Check into neoprene foam, it's the stuff they make can coozies out of. Its got TONS of uses, and makes killer seat padding. Wrap in pleather of your chosen color, and ride comfy.
Oh it can be had in various thicknesses, and can be sculpted. If need be, use layers, cut to shape, stack and glue.
By shrinking the layers a little at a time, you can control the taper of the finished seat easily. Take it a step further by using holes, divots and ridges and the seat can be tailored to your, ahem, junk.
I've done a few ATV seats like this.
Your tank looks good, i think a springer of some form up front would look sweet, but I'm fond of their aesthetics myself.
I ride a Hurricane with an SD Stinger as my sole transport, check your welds close, but my bike is solid. What welds would worry me most, would be any that look like play-DOH or bubblegum rolled out and laid in the seam/joint. Any that have excessive "buckshot" or BB like splatter. Any that look to be lying in an eroded valley. Respectively, under-penetration, incorrect arc distance, and over-penetration.Also look for any voids, or obvious major variations. If you can weld ignore all of that, and pleas accept my apologies for all that.
Regardless, as best I can tell my bike was hand welded, meaning an inexperienced welder could do all of that and more- on the same bike! A robot typically goes out of calibration and builds the whole frame (read "batch or lot") with the same bad welds. For instance my freind, Stacy, owns a huffy cranbrook, with no penetration on any of the welds. Robot was out of calibration. Thank Gods it's just a peddler. If your hurricane was hand welded like mine, check them all, if in doubt post pics. No matter what chech your welds, again!
Gitrdone! Good luck!