My advice would be to stick to the plans. As mentioned, it’s very easy to have the wing spar sitting on your work bench, check and shim for zero twist and clamp it in place before doing the top skin. You would definitely want to have the spar held in place while riveting the l.e. which wouldn’t be as easy. And how much time are you really saving between the two riveting methods.
Triple check that all your rib flanges are square to the entire depth of the web, not just the last 2 or 3 inches or you’ll have oil canning. Ask me how I know