Give everyone six hours and let kids leave when they are done.
The only reason why you have the accommodation issue is because the test bakes time pressure into the equation. So kids/parents strain to get extra time because it is an advantage. And many kids who deserve accommodations can’t get them. Give everyone the opportunity to have up to 1.5X time and that all goes away. The smartest kids will still get the highest scores. The kids who don’t need the extra time don’t have to use it.
Speediness is certainly a relevant factor in some lines of work – 100 meter sprints and hitting fastballs – but to me it seems pretty unrelated to being able to do college level academics.