Now that's what I like about this place, everyone is ready to invent ways around problems and share the results. And with modern technology, tools that used to be very expensive for your hobby mechanic are now possible with this sort of thinking.
I made a "camber gauge" as well although I'm not brave enough to show my efforts, which were/are much, much cruder.
I took a 3/4" (?) steel box section and cut it to exactly the wheel rim diameter, one layer of insulating tape around each end to stop scratches and then used a similar gauge to show the angle. The hi-tech difference
is that mine's got a magnetic base so you just plonk it on the steel and it's good to go. This ultra crude example only works if the profile of your alloy wheel doesn't protrude out from the line of the rim, in which case you'll need adjusters like yours.
My only serious comment would be not to go too cheap on the gauge, from what I found the accuracy is good on 99% of gauges at the 90/180 marks but errors creep in as you move away from vertical or horizontal. Probably not enough to cause a problem for us with 0.5deg allowance but even so it's worth avoiding the really cheap stuff. And the trouble I have is that once you find you can measure to 0.1deg then you try to adjust both sides to 0.1deg !!!
Just thinking about it, this sort of thing would make a good stickie in the garage section, something like "DIY Equipment" where folks have made things like this, alignment kit, spring compressors, transaxle nut tools, etc. Descriptions & pictures, that sort of thing. If we refrained from adding comments, just descriptions, it might help out newbies to these cars and their quirks.
Brian