I'm thinking of buying a new domain and make 100 subdomains under it. The top domain will be a big niche while the subdomains will be small niches that is related to the top domain. I'm thinking of building a link pyramid to each subdomains cause the top domain will just be a link directory linking to my subdomains. Do you this backing inky strategy safe? Will I get good rankings if I did make link pyramids to all of my subdomains?