We did consider this, in fact in early pre-beta builds thats how the powershell action was implemented. The reason we changed it is because we are trying to avoid windows dependencies in the agents, as we hope to have agents running on other platforms using mono at some point. We will revisit this in the future as it should now be possible to have agents with different sets of actions due to other architecture changes since we made that change.
I’ve been thinking about this a slightly different way. In my repositories, I’ve added a {myrepo}\ci\ folder to include all the finalbuilder components etc. However for upgrading web sites, I have a couple of powershell scripts that automate IIS tasks to configure a maintenance site during upgrades, so Joe Public doesn’t have a bad user experience. I figured I would be able to use Continua and powershell using that approach. Just my two cents.