Customizing (design and functionality) an existing wordpress site

I would like to do add a few functionalities and zip up the design of an existing wordpress site. The site is here [login to view URL] and it is a wall of ideas where people can post, edit, comment, like posts with • New functionalities: one password login without registration • Add two more fields to the ADD IDEA form • Add (re)edit function to all posts • Add a print function to all posts (print a pdf card of singular ideas • Add a print selected function that let#s people select specific posts from all posts and prints them as a set of .pdf cards • Re-organise rights: everyone should be able to edit posts (with an edit button next to the comment, like and print ones • Add searchbox that does predictive search on tags and full text • Clean up the design: new font, some mouseover effects, clearer organisation of posts on page, add background image. Better proportions between images and text… • Ensure that full functionality across platforms, mobile etc. is maintaine along the way