I think Arc's load time is pretty typical of uncompiled Racket code. In Racket, people can speed up their development process by using `raco setup --pkgs my-package` to compile their libraries or `raco make filename.rkt`
to compile individual files. That might be harder to do for Arc, especially the Arc REPL, since Arc's macroexpansion is interleaved with run-time side effects.
I'm not sure how to answer that. If you're asking what the easiest way would be to speed up initialization, it would be to load fewer libraries. Since it's an anarchic fork, we've all added lots of ideas that are good in principle but not always needed.