I've got a wonder here, about Psychosomatic Surge and its ability to grant temporary HP. Could this at all be used to keep a person who had gone below CON in negative damage alive?
Would such a person be able to benefit from normal healing?
I don't think so. Temporary hp are always lost first. So either the temp hp are added, the target gets hit, then loses the temp hp; or the target gets hit, dies, and it's too late to add temp hp. Unless Psychosomatic Surge has some special wording I'm unaware of.
Of course, if your con actually hits 0 due to damage... You're still dead no matter how many temp hit points you have. Even if you do actually have hit points left, for example a level 6 kineticist with 14 con who take 14 con damage but no lethal damage, con of 0 means "you are dead".
I figured, just thought I'd also point out that if con drops too low, you're gone no matter what. And your example would also suck Wendies frosties through a too narrow straw. Aka really really hard.