Complex sentence: I proposed that if engaged to write a Wikipedia article, I could write it in my sandbox, then invite a member of the Wikipedia community to independently review it and if it meets community standards, they could move it to mainspace.
Split into simpler sentences: I proposed that if I am engaged to write a Wikipedia article, I could write it in my sandbox, then invite a member of the Wikipedia community to independently review it. If it meets community standards, they could move it to mainspace.