I was the one who mapped Stage 1 several years ago. I always meant to go back and finish it since it is my favourite Contra game but I guess it just fell by the wayside. I fully intend to map it completely but unfortunately, thanks to having many different projects going on at the moment, you might have to wait several months, if not a year. I'd be sad to see someone else do it in my place but it wouldn't be right to claim the "exclusive rights" to map this game while not actually doing it over several years.
In short, just know that I really want to go back to it, but it will be a while unless someone else does it first.