win2k3 AD site topology

Hi All
I have been tasked with restructuring a win2k3 AD site topology, we have around 25 sites with a DC with WAN links, already we have got a auto generated site topology but this is not the hub and spoke topology we want,

My question is can I create a site topology (the hub and spoke setup we want) along with the existing (the auto generated ?default site links?) and increase the cost of the default links and then delete the default site links after a while. What can go wrong or is this good setup. would appreciate any suggestions

thanks