Magical skills (some of them anyway) do not necessarily require a mod or even a teacher; even books will do for some, though they'll give ridiculously low experience if you start from zero. The design choice behind this stems from years of experience with PbP and watching generations of moderators burn out training PC after PC in the same things ad nauseam. It's especially true here where we have a limited number of mods at the moment and most of them are busy developing the world. It's a fact that if you say yes to PC #1 you have to say yes to PC #2 and so on. Before you realize it you've got half a dozen training threads that take up your time - time that could be better spent writing actual plots. Then, if you slow down, PC's start being annoyed at your holding them back whereas mod #2 in the next city posts so much faster! That's when it stops being fun.
(I'm not even mentioning how requiring a mod would lead to PCs with 10 magic skills at 5 points each in their starting package... 13 for humans. Solution being worse than the problem.)
I'm going on a slight tangent here, but my vision for Mizahar was that of a hassle-free game, and as grind-light as possible. In the ideal little world inside my head, your PC mostly trains
offscreen and shows off in fun threads that other people may actually want to read. We aren't WoW, we don't need the grind - if you write about your skill and you do so well, you improve. So you want to learn magic fast? Great, have your 2 XP. Now try bringing them to a fight without further thought put into it, and watch your head blow up (well, you can't really watch that, but still!) Yes, you can easily die from using magic carelessly. Taking magic = signing a waiver for it to mess you up.
Right now, the only skills that are restricted are those revolving around interaction and roleplay - such as Gnosis and Familiary. Honestly, instead of forcing everyone through a system that we can't maintain, I'd give rewards to those who go the extra mile and actually seek out a teacher who's the best at what he does. (Note that skills requiring a laboratory already force you to do that). Maybe a starting XP bonus granted by mods?
Also, there are truly ultra-rare skills that
will require lengthy quests to be learned. I already have a short list... for example, see
Lost discipline...