Joshua, you are not paying attention to the way SAS works.
Each SAS session/instance creates a temporary WORK directory/and files. The base location for this is defined in the sasv9.cfg configuration file. So each physical server is going to have at least one place where this "workspace" is going to be. You have no choice in that matter. Minimally, SORTDEV is not defined, so WORK is used. What you have to be careful of is SASUSER, which is persistent, and EG tends to want to use this space, which will get confused and clogged up. This is irregardless of where the metatdata respository sits. The metadata repository has nothing to do with "workspace".
It is my recommendation to set a policy to use "Assign Library..." to create EGTASK for each project, and to keep each EG project and its related files (query results) in that specific directory/folder for that project. It'll make for easier maintenance.
If each server has only 400 GB of space, and that is all local disk (no SAN space), then you may run into space and performance problems, especially as EG work accumulates, and if there are any significant datasets. You and management cannot be chintsy here, or you're asking for a lot of extra work, and disgruntled users.
That is my opinion.