I am fairly proficient in building WP sites, I am looking to create a new type of site however, and am not fond of the idea of being terrified by WP updates screwing up my site or using plug ins w developers that fall off a year later so on and so forth. I need stability/security to be effortless if possible. The site I want to build will have its own content but also hold a network of smaller sites, allowing each sub-site to have capabilities of updating content on a regular basis whether it be videos, 'posts' or podcasts. I am looking for input on wp - multisite alternatives. I would like the main site to possibly have forums, but am open to putting the forums on a subdomain and linking them to the site or doing some sort of work around.

Any suggestions on a more stable CMS that can be used to make this happen?