@AndrewLeach Yes, certainly you can construct a sentence with a participle as the head of the clausal subject, but under most analyses it’s still an adjective, not a noun. Syntactic evidence for this includes that it’s modifiable by adverbs like
recently not by adjectives like
recent, plus isn’t morphologically plural nor can be made so—unlike
givens or
fixings. The simplest explanation is probably the one where it’s all that’s left over from an elided plural noun like
people or
things. Terminology ranges from OED’s “absolute adjectives” to CGEL’s “fused modifier-head NPs”. —
tchrist 4 mins ago