Create a custom plugin that will change the default WYSIWYG editor behavior for posts

My site is avelim.co.il. The site is on Hebrew wordpress 3.5.1, using the theme Weaver II Pro 1.3.2 My test site is [login to view URL] What I need the plugin to do: Currently, when you start entering a post and then publish it, the text is aligned to the right (Hebrew is Right to Left). I need this behavior to change. I need that when you start typing a post the text will by default be aligned Center. You would be able to change this for a certain post, or part of a post using the WYSIWYG editor. This new feature should not affect the way that pages ot comments behave (I have a custom plugin that puts a WYSIWYG editor in the comments dashboard). The changes requested will only affect posts. Work should be done in 24 hours after being awarded the project. Freelancer should send me a zip file of the plugin to install. Freelancer should allow 7 days for testing after he finishes his work, before getting paid.