(a) simple solution - yes
(b) to overlooked problem - no. It's just a personal spin on Lisp/Scheme. It covers exactly the same territory.
(c) that actually needs to be solved - no. Programmers have many good languages to choose from. Arc is a nice little wrapper on top of Lisp to make it pretty, but any undergrad could do the same thing.
(d) deliver them as informally as possible - no. You don't write long essays about a language 5+ years before you show a prototype if "informality" is your goal.
(e) starting with a very crude version - yes
(f) iterating rapidly - no. You could get a master's degree in computer science in the time it took for the minimal prototype of Arc to show up.