I think you're planning far too ahead. I don't want to come across as a preacher or something, but as any other language lover I used to want learn a heap of languages too and was telling myself that each year I'd learn one, but the reality is different.
You should concentrate on the closest target, which should be a language that you want to learn the most (it's a bad thing to postpone say Japanese, because it's a lot more complicated than say Spanish, if you really feel like learning Japanese).
Anyway I wish you luck on your journey.
As far as I'm concerned, the Arabic script seems much more difficult than it actually is. I had some problems with remembering Sad, Dad, Ta and Za, but one day I stopped trying to remember the alphabet and was looking at words and their transliterations and sooner or later found the patterns. So now I can read (slowly) the Arabic script, but the problem is that it's only like 60% efficient, because you have to guess the vowels which are badly if at all indicated. Anyway it's fun to read the Arabic on a bottle of chocolate milk etc.
Mandarin Chinese is a total suicide and it's more than possible to burn out after a few very exciting months. But that is valid for any language in which you achieve an intermediate level I guess.
Wish you all the best once more
Zippo