I've seen it done, but not well. A decade ago there was a failed attempt with a web-comic called "The Mystics" which featured obscure Timely characters like Elecktro, the Ferret, Rockman, USA, etc. which the author assumed were in the Public Domain. Unfortunately his artistic and writing skills were not up to the level of his ambitions. He was also using an obscure domain provider who I believe is not defunct.
The idea is sound. and there have been web-comics done in the golden age style, and even set in the thirties and forties but none that I know of that featured public domain characters in a serious attempt to recreate or reinvent golden age characters.
Be interesting to see how long this thread lasts.
Intrigued,
Jon