The thing is how does a trainer unlock those skills for you?

Assuming you have a reached the appropriate level..you go to a trainer and he say i can teach you a new skill.

If you agree you have an option of

A) Accepting a quest(set in the battlefileds arena..or an alternate universe..using portals to enter). These quests will test your ability by using existing skills(not the one you want). By completing this the trainer unlocks the skill for you.

Advantages: You get Expereince by killing any monsters plus expereince of solving quest.
Disadvantages: Might take a while to complete the quest.

B) Paying the trainer to unlock skills for you.

Advantages: You get the skill instantanouesly.No need to wait.
Disavdantages: Your purse is lightened plus you will not get any expereince/items by this method.

C) By pratciing the skill.
Here the trainer allows you access of a skill you want. Then you have to practice it or if thats not possible to read about it and then the trainer will test you knowlegde.

E.g you want to learn say fireball...the trainer then you temporailry gain the fireball skill...but you must practise it on a dummy.
So you cast the spell...now here is the catch. The spell may or may not work.
f it does you get a message or your character says "ive done it".
If not your character says" hmm it doesnt work".
To gain the skill you must sucessfully cast say 25 fireballs. Naturally the higher intelligence you have the more likely you will be sucessful.
Or if say you want to learn "hide in shadows " this may be difficlt to test in practice so the trainer gives you a book and you have to read and learn how the spell works.
The trainer will then test you. If you get the answers correct you get the skill and a reward a good item.

Advantages: A good item of your choice..e.g you may feel your boots are horrible so you select boots from the reward list.
Disadvatges: Can be boring and you need to be patient. May take time to complete as well.

Well what do you think?