That all sounds good to me - I was wondering though if that syntax was valid in ACF?
ACF 20128 U5 only allows the parens to be optional if there is no type or default specified.
Adobe 2018 update 5 came out today and supports this syntax. Transitioning this ticket to an incompatibility.
Here's a set of tests that show all known bugs in Lucee and Adobe CF's fat arrow functions along with a reference implementation in JS where everything passes.