If I understand what you were trying to accomplish with Arclite (and that's a big IF, Russell) Suffusion would be able to do the same thing. It has a custom CSS area that allows you to make changes, but still does not interfere with theme or WP upgrades. Atahualpa had one also, but I'm finding that Suffusion really allows me to make more customized adjustments than I ever imagined being able to do without coding.

And all those templates really make things almost too fun. . .