Good idea Max - looking forward to seeing how it works, but there may be some issues making it work like "reality".
I have never used the second type you are making, but the first one is looking good as a basic studio umbrella setup. The light is adjusted by sliding the umbrella closer or farther from the light, which makes the reflected hotspot bigger or smaller, and thus makes the light source bigger/smaller and the shadows softer/harder.
They also come with white, or silver or gold reflective surfaces. That makes the light harder/softer too, and warmer/cooler too.
All that is assuming you are using a black backed umbrella and bouncing the light back towards the direction of the strobe head. If you go the other way you take off the black backing and you have a shoot-through umbrella, which is basically just a softbox type light, but with some flexibility in how hard the light is.
So, once you have your shapes built it really becomes a big question of the materials you use, and then how Maxwell handles all those reflected caustics
My feeling is that you will probably want to use a normal emitter and just have the umbrella prop there to create more realistic detail in your reflections, but not as an actual light source.
b