> I think that’d leave int addition and multiplication, and I don’t think there’s anything else offhand. Other than those, require parentheses.

At this point you just require every compound infix expression to be parenthesised, the terseness isn't worth the inconsistency. Especially as, as others have noted, these operations are only associative when working in some classes (notably not necessarily when dealing with floats).

And then you do automatic parens insertion in the LSP, so you write

    a - b - c

and when you save the lsp fixed it up to

    (a - b) - c