It seems like a bad idea since the whole point if the CuAl stuff is galvanic corrosion control. Any time in industrial where someone say gets a wild idea and puts a split bolt on a copper line to connect to aluminum utility wire. Within a couple years everything dissolves.
The split bolts made for copper and aluminum have a divider so the copper isn't touching the aluminum, this seems to be a pretty bomb proof way to deal with the issue.I just went on a service call where the house lost one leg. They had a service change three years ago and the electrician used copper split bolt connectors and exactly what you said happened. The Aluminum wire was completely corroded away. The Utility gives licensed electricians the right connectors for free and they allow us to make the proper connections.
The purple wire nuts rely on the antioxidant grease to inhibit corrosion and the give in the spring to deal with expansion and contraction. That sounds like the kind of thing that works most of the time.
Again for small wires in crowded boxes I think the lever nut has the most potential if it has or gets the necessary listing.