I don’t think it’s pure coincidence that Sartre would suggest a core existentialist notion–that we are our choices–and I think this is because he inherited the subjective theory of value from the Brentano (Menger) tradition. Without doubt, the existentialists had an implicit methodological individualism as well. I agree with those who say that Sartre’s Being and Nothingness was a “brilliant misunderstanding” of Heidegger, and this early work, before Sartre’s attempt to integrate Marxism, would probably yield some insights for an Austrian. Sartre’s later work likely had a lot trouble partly due to the inherent conflict between the subjective theory of value and the labor theory of value.
Despite his evident Naziism, the current intellectual scene takes Heidegger much more seriously than Sartre, and along those lines, I think Being and Time can yield a lot of insights, not the least because Heidegger’s deep analysis of how we relate to equipment and live purposefully though coping. Heidegger had similar neo-Kantian influences to Mises and Weber, and he also stands within the Brentano tradition, so there is much to ponder. I also think that research into others like the early Paul Ricoeur and Ortega y Gasset could yield good things. Ricoeur, for example, addressed the “human action” side of phenomenology in a similar way to Alfred Schutz.
https://forum.freecapitalists.org/t/illegitimate-disturbance-a-brief-introduction/18716