Zenx showed you the way, but since I'm also doing similar thing I thought I'd share it:
I have all my abilities made with data (some are mixture of triggers/data, but it doesn't mater) + dummy abilities (for hero).
When you chose to assign ability to a spellslot, you replace buttons info, ability costs (cooldowns/charges/vitals) and launch/cursor effect.
Button and Info are done through catalog get/set functions, launch/cursor effects need to be replaced with "Catalog Link Replace".
Since you're replacing effect links you'll only need 10 dummy abilities (5 for target spells, 5 for instant effect spells). All of your target spells will need to have a range indicator and cursor AOE effect. For spells which don't use AOE cursor simply assign a dummy search effect where all players are excluded (player/ally/enemy/neutral).
If you want to have a toggle-able abilities (like ghosts cloak) you can emulate them with Effect-Instant.
There are limitations which come with such system, since catalogs can't really modify anything other than cost, cast/finish times, launch/cursor effects. You won't be able to adjust flags, auto-validators, placement units, spell phases and other things. So design your spells accordingly (for example if you have a multiphase spell, make phases with behavior chains). Another painful thing is that you can't transfer requirments. So if you have a spell which originally summons up to 5 units (and if all 5 units are alive you can't summon more and icon is grayed out), if you transfer spell into this system you'll need to use triggers to manually disable/re-enable spell.
So, some thinking is required, but overall it's nothing complicated =D
Edit: that link to Renees topic is interesting, I would wait to see if you can achieve your goals by playing with spell-items, too bad I know nothing about that and since I've already made my catalog system I'm sticking with it :D
Zenx showed you the way, but since I'm also doing similar thing I thought I'd share it:
I have all my abilities made with data (some are mixture of triggers/data, but it doesn't mater) + dummy abilities (for hero).
When you chose to assign ability to a spellslot, you replace buttons info, ability costs (cooldowns/charges/vitals) and launch/cursor effect. Button and Info are done through catalog get/set functions, launch/cursor effects need to be replaced with "Catalog Link Replace".
Since you're replacing effect links you'll only need 10 dummy abilities (5 for target spells, 5 for instant effect spells). All of your target spells will need to have a range indicator and cursor AOE effect. For spells which don't use AOE cursor simply assign a dummy search effect where all players are excluded (player/ally/enemy/neutral).
If you want to have a toggle-able abilities (like ghosts cloak) you can emulate them with Effect-Instant.
There are limitations which come with such system, since catalogs can't really modify anything other than cost, cast/finish times, launch/cursor effects. You won't be able to adjust flags, auto-validators, placement units, spell phases and other things. So design your spells accordingly (for example if you have a multiphase spell, make phases with behavior chains). Another painful thing is that you can't transfer requirments. So if you have a spell which originally summons up to 5 units (and if all 5 units are alive you can't summon more and icon is grayed out), if you transfer spell into this system you'll need to use triggers to manually disable/re-enable spell.
So, some thinking is required, but overall it's nothing complicated =D
Edit: that link to Renees topic is interesting, I would wait to see if you can achieve your goals by playing with spell-items, too bad I know nothing about that and since I've already made my catalog system I'm sticking with it
:D