Throw everything open and let the public in, because, public is small. I am of half a mind to say that beta should be open for everyone, because first of all, it's a non-commercial product, second of all, our community is tiny.
Most if not all of the development team is for this. However there are some logistical problems we currently have with doing this AND that we will always need an internal beta team to catch some issues early to prevent larger community scale tests from being ruined.
I believe we want to run a public open beta test at least once a month.
However how do we realistically do it in a sustainable manner? We can't give everyone access to the SVN, it doesn't have the throughput or capability to deal with that and the amount of issues beta testers have would compound drastically with a larger section of the community. It also requires drastically larger harddrive space than the main build.
We can't really expect people to copy existing versions of MB2 over and download a "changed files" zip every release, and it requires a few hours to put that together, upload to multiple places, and verify. The same with upgrading via a full download being a problem as that takes more uploading time, takes people forever to download, etc.
The launcher capability to run open betas won't be available for a long time as we don't have the programming resources for that.
I think the closest thing we can do right now is uploading the build to github and updating what we need for testing. That way it auto generates a zip download for the lazy people and for those experienced enough can sync and only download changed files via git + lfs.