In any solution available there are costs to pay (economical or temporary ones).

So I could write the code missinig, if the time required to write the filesystem sincronization and the session state handler would be a month.

For more than a month the economical cost would be (more or less) equal to the prebuild solutions in the market.

For writing the session state handler over 9P I estimate a week...
If a sincronization system for the grid nodes (or a sintetic filesystem providing access to the grid and replicating writes among node) would require more than 3 weeks of man work probably I've no chance to get this solution approved.