Theory 2 is viable if you believe it can attract links better than trying to attract them to the main site. For instance, there can be a limit to how much content and what kind of information can be placed on a corporate web site. Some may feel a blog is not appropriate for their corporate site.
It's also a viable strategy if the main site already ranks for target phrases and you wish to create a useful resource to rank alongside it. It will need to rank on it's own usefulness and ability to attract links. If it can rank for your target phrases then it has earned that rank. The counterpoint is that it might not be as easy you believe and as mentioned by buckworks this method could be squandering an opportunity for attracting links to the main site and cementing it's position in the SERPs for the long run.
While I would prefer to have those resources on a single site, there are legitimate reasons to have a satellite site. Returning to the question posed by the OP, I don't believe creating an extra site for the purpose of creating another inbound link is a viable strategy. The energy/time/money expended on the effort would be better utilized in building genuine external inbound links.
Just my opinion but I think the best reason for creating a satellite site is if management restrictions on the main site prohibit the creation of forums, blogs, and other kinds of Internet dialogue with the public.