> The table-like syntax is nice, but it has the following problem. [...] Unless I'm missing something, there is no way to have ssyntax for the part after the first set of parentheses.
Yes, this is sometimes a problem for me too, or at least an annoyance. It's one of those things that's a bug or feature depending upon who you ask, though.  Whichever way you classify it, the root issue is with Arc, not the compiler, which just conforms to Arc's ssyntax rules.
Interesting formulation, but the inner parens' inclusion of value makes it look like value is another argument in the function call. It also might be too similar to dotted cons notation, e.g. '("foo" . value).