As I understand new domains usually ones that start attracting lots of traffic get sandboxed sometimes even up to 6 months. So what I wanted to know was, wouldn't it be a good idea to launch domains that you might have that are not ready with a one page site with some relevant content? Although it is a one page site atleast when you are ready to launch your official site you will not have to wait for your site to come out of a sandbox phase. Do you think this is a good idea and will it avoid the sandox issue for your official website when ready? Is there any way this can damage my website ranking or future SEO work? Thanks
Doesn't matter, it's the web pages that get so called "sandboxed" most of the time. Creating a one-page domain isn't going to give you the effects your looking for. Googlebot will notice the complete change when your site goes live and probably consider it a "major" alteration (this is my words) and give it the same new site status. This is why when people make template or internal structure changes they see a temporary drop in their search results.