Just learned about these family of CPUs, which have Alder Lake E-cores only, with a very low TDP (6-7W) for Skylake-level single thread performance:
They should work well with passive cooling while providing much longer battery life than 35W processors. I’m very interested if Framework can make mainboards for them, for both ChromeOS and Windows 11.
Given that the efficiency cores are not super efficient you are probably better off just tuning the 1240P down (disable turboboost). More cores at lower speed is usually more efficient under load. Apart from cost that should be a similar or better solution, depending on the workload.