Plugins for WordPress as a large scale CMS

I’ve got an upcoming client at the start of the year that needs a new website. The old design stinks and isn’t mobile friendly. This website has a minimum of 100 pages that I’ll be creating, though I am sure there are more hidden I haven’t found. Because of this, I suggested Joomla because I believe it is a stronger CMS for large scale websites. The boss man said no, they’ve always built websites in WordPress and he refuses to learn a new one. I’m not here to start an argument over which CMS is better or to bad mouth my boss. All I want to know are some suggestions for good plugins to beef up WordPress as a CMS. Below I have listed out some of my major problems with WordPress I have had over the past year developing websites with it.

• I hate the drag and drop menu system for wordpress. I find it slow and very picky with nesting menu items inside others
• I want to be able to sort the pages into categories better. For example if I am in the about us section, I want a drop down to select ‘about us’ and it only shows me pages in the about us section.
• WordPress seems to run slower then Joomla, especially when I open multiple tabs. Is there anything I can do without changing the server to make WordPress run smoother?
• I hate that WordPress automatically adds <p> tags instead of just wrapping everything in <p> tags. This is a compound issue because in Joomla when I look at the source code, it is color coordinated much like Dreamweaver. When I move source code from WordPress to Dreamweaver, I can’t apply source formatting and everything is a mess. Is there a plugin that automatically adds the <p> tags instead of the way WordPress does it now?
• Are there are any general plugins I should use when making a large scale WordPress site?

Thanks for the help guys! And let me know if this should be in a different subforum.