Is there a way to have a single set of DNN dll's when hosting several sites with their own DNN database? It seems it's a waste of disk space and more importantly memory and CPU resources to have the same DNN dlls loaded in memory for every site when all the sites are using the same version of DNN.

I am not sure if one of these solutions work with DNN
1- Put the DLLs in a folder and have the web.config assembly location setting point to that folder for every site.
2- Install the assemblies in the GACSubmit