FFTA magic system type thing

I got ffta(final fantasy tactics advance) a while ago and its magic system is based on items, if you have the fire rod for example you get fira and if you use it enough you learn it and no longer need the item. i was planing on doing something like this for my map. it works the same way, but once you have a spell you can level that spell up without other items and such.
If you use an item/spell for say 20(an example, i have no idea what to make this number) times you learn it. once you have it, say you use it 10 times it levels up. etc...
Is this agood idea? bad idea? Comments?

Good idea. I have FFTA and was also going to try that method out but have no clue how to make it work. I will explain if in more detail for anyone who wants to help but hasn't play FFTA

Equip Rod -- Can use Fire
UnEquip Rod -- You can not use fire

it is like this till you gain a number of AP (like XP but for skill learning only)

After 100 AP has been earned

Equip Rod -- Can use Fire
UnEquip Rod -- Can use Fire

The amount of AP changes. The better the skill the more AP.

100 - easy skills, 200 - medium, 300 - best skills, 999 Ultimate skills

Also you can learn things from any wearable equipment but useable items.

Seems easy enough.

E: Unit acquires item
C: Item = fire rod
A: If FireRoduses < 10
Then Add Firebolt (or whatever) to Hero manipulating item

E: Unit loses item
Unit sells item
C: Item = fire rod
A: If FIreRoduses < 10
Then Remove Firebolt from Hero manipulating item

(these two deal with the novice depends on item. If they already have the skill permanently, then these triggers will no longer have any effect).

E: Unit starts the effect of an ability
C: Ability = Firebolt
A: Set FireUses = FireUses + 1
If FireUses = 10 then
Remove abilty Firebolt
Add ability Fireball (or whatever)
Display text to player: Your skill in Fire has improved

etc. etc. etc. You'll need to do this with all of your skills.

One problem I see with this is that there is no way to "forget" a skill. I.e., once they've used Firebolt 10 times, they'll ALWAYS have that ability. Which may not be a big deal, but if there's more than, say, 2 skills, somebody's going to be upset that they'll always have the first 2 they gained.

or even easier just make the firerod have the fire ability....
then after 10 uses just add ability
and as for removing skills,i have a system planed out... a very annoying to make system..

I'd be careful about that; otherwise, every 10 uses they'll get another copy of whatever skill Firerod gives. You should probably stick to an internal variable that only allows giving a skill at 10 and exactly 10 uses.

As for removing skills, I suppose you could just remove every skill in that tree. Have beacons for add and remove - if they walk into a remove beacon:
Action: Remove ability Firebolt from entering unit
Remove ability Fireball from entering unit
etc etc.

If they don't have the ability, then there will be nothing to remove, so nothing happens. You can simply remove all of the relevant skills and not worry about checking if they have it or not.
Adding them back will be a little more tricky. That, you'll want to check their FireUses variable to do. If it's <10, do nothing, if it's 10-20, add Firebolt, if it's 20-30, add Fireball, etc. etc.

dno't worry ican easliy trigger this... I am just not sure how useful it might end up being...