This is so cool, @svan! I love this, thank you for sharing it.
With the py5_tools.processing.download_library() feature it becomes even easier to use it, you don’t have to manually copy the jar file!
Check out my attempt at simplifying a bit the sketch:

# Uses Imported mode for py5, learn more at <py5coding.org>
# To install the ControlPy5 .jar, you only need the following two lines once
from py5_tools.processing import download_library
print(download_library('ControlP5')) # printed to see details of how it went
from controlP5 import ControlP5 # on module mode, this must come after import py5
def setup():
global slider, cw
size(450, 450)
window_title("DotView Demo")
this = get_current_sketch()
cp5 = ControlP5(this)
slider = cp5.addSlider("slider", 0, 255, 50, 30, 10, 200, 20)
cw = cp5.addColorWheel("c", 300,10,100)
cw.setRGB(color(128,0,255))
def draw():
background(209)
fill(cw.getRGB())
circle(200, 220, slider.getValue())