Thank you for your post.
I'm certain your experience will serve you well in getting published, and I wish you luck! The For Dummies series requires you work through a literary agent to submit material. I've included a few links below, which will be good review for working with Wiley in getting content to your readers. I can't for sure say we don't already have titles within those topics, but your agent would be the best person to speak with regarding topic development for generating publisher interest.
If you're looking to compose a custom book from existing Dummies content, you might also check out: Create Business Solutions with the For Dummies Brand and How-to Content - For Dummies
I hope this helps! Please let me know if you have any further questions. Have a great day!