I'm sure I'm not the first person to suggest this. ;^)
Everyone who's a programmer knows what camelCase is. That's when you use capitals in the names of variables or functions to make them more readable. For example: setLength() or startsWith().
You can probably see where I'm going with this in German.
Consider a simple number like 19,764. In German, it's neunzehntausendsiebenhundertvierundsechzig. Now, wouldn't it be more readable as neunZehnTausendSiebenHundertVierUndSechzig?
They already capitalize all of the nouns anyway, so why not go one step further? For example: "der Waschmaschinenschlauch" => "der WaschMaschinenSchlauch". Better, no?
It would also help with those crazy separable verbs. If you haven't studied German, you may not know that there's a whole class of verbs with prefixes that are sometimes attached, and sometimes find themselves on opposite ends of the sentence...
Take "zumachen" (for closing something like a window). You can say "Ich will das Fenster zumachen" or "Ich mache das Fenster zu." In my fantasy universe, it would be written "zuMachen".
Anyway, if any of you have access to the person who's in charge of German spelling/grammar rules, please be sure and suggest it. ;^)