The problem of doing this is: after the construction of the Scale Free Network if some nodes have more edges than the cache size what you do? How do you remove edges?
Furthermore, to build a Scale Free Network using Barbarasi-Albert algorithm when you have to add nodes to the random graph, you have to choose m where m is the number of edge to create for each node you add, so you can limit it to the cache size if it's greater (i have done like this).