Sync and build fast code from large repos

Hi,
I'm starting to work with continua. My problem is now that i have to work with two large svn-repositorys (3 - 6 GB), which are uploaded to my agent-cache. But everytime when I build a stage all data is copied from the agent-cache to agent-workspace and this takes too much time.
Is there a way to omit this copying from cache to workspace?

My idea was:
  - checkout the repositorys on my agent.
  - save the path to this repo in a system-variable.
  - check on server with a propertycollector if this variable is set on my agent.

and on each build:
  - cleanup the svn-repo on path of this system-variable.
  - update svn-repo to needed revision.
  - work on this local svn-repo instead of the workspace.

My questions are now:
  - Can i do this whit continua?
  - Or is there a options so that the agent works direcly on the cache and not on workspace?
  - Is it a good solution or are there better ones?
  - Where can i get the svn-version (e.g. which triggered the build) to which i have to update my repo on agent

sorry wrong forum - moved to ‘ContinuaCI’ forum

Thanks we will deal with it there.