You are comparing apples to oranges. WordPress is a platform, Ruby is a web framework. If you are looking to develop a completely custom platform, you could certainly do it in Rails, but you could also write it in PHP (like WordPress).

I'd do some digging and see what is out there for pre-made software first before you build something from scratch. I'd imagine there are already plugins that would do this sort of thing for Expression Engine, Joomla or WordPress. No need to re-invent the wheel!