One reason current L/D is about “permanently alive” and not “permanently dead” is probably J89 L/D example 2. There two B stones in the corner are capturable, even permanently, yet not dead (as they give rise to new permanently alive stones nearby).
Sure, but this assumes that taking the ko is a step forward, or improves one’s score! Which feels natural and is true normally, both under area scoring and (noseki) territory scoring, so the players are interested in continuing the repetition.
But it is not true under noatari-territory scoring (at least with the standard L/D), where every ko capture decreases one’s score by one. I think this reflects some of the risks of not excluding sekis and allowing dead stone removal from there. Territory scoring is just safer without them.
I’m not against new L/D approaches btw (mentioned one here), but until you define a coherent system based on “permanently dead”, it seems too early to rely on it for analysis of a different idea.