Why do you think first-person experience is fundamental? It seems to me it's way more likely to be an aggregate phenomenon, like fire. There's no low level fundamental fireyness, it's a chemical reaction like any other, we humans just label reactions that meet certain criteria of scale, setting, and composition as "fires".
> Some supporting evidence is that first-person experience in sentient systems, as far as I've observed, is usually motivated to preserve sentient systems
I suspect this has more to do with the fact that you are far more likely to observe systems that seek to preserve themselves, since they are more likely to continue to exist. It doesn't indicate an emergent behavior of sentience, it's just observation bias.
An emergent behavior is a macro phenomenon that arises from simpler ones. We can say that an emergent behavior exists if we can find just one example of it, so the probability of it happening isn't as central. However, establishing for one example that both a structure and its components are sentient is a tall order -- each of us knows only one first-person experience first-hand. We can accept that we are sentient, but could we conclude that each tissue and cell has its own experiences? Thinking about the subconscious helps persuade me that it's possible.
Not all carbon exists in crystalline form, but just one example of graphite or diamond makes properties of carbon atoms apparent.
For example, matter isn't formed by the composition of atoms, atoms are already matter to begin with. And due to various physical properties of atoms, they compose together. This is reasoning by analogy, which is inductive, but at least the line of reasoning is more consistent with what I understand about other areas of physics and logic.
It seems much more plausible to me that there would be some fundamental component of first-person experience. The sentient components could then compose together into complex sentient systems.
Some supporting evidence is that first-person experience in sentient systems, as far as I've observed, is usually motivated to preserve sentient systems, which indicates an emergent behavior of sentience directing motion and energy to orchestrate a self-perpetuating system, rather than the reverse.