Can I savely erase these Avilities?

[crazybayman]

Wee, that´s also possible?
You mean like changing the Dagger with the Mage Masher in FF9,
since the latter has all the stuff from the earlier, but even more (higher Strength & Detect command)?

Exactly.

I always stuck to things like Magic, Draw and Item; those super-common things, as it felt pretty secure.
But now I´ve got even more possibilities, it seems.

Most definitely. Recover for instance, which I think it an ability learned from Leviathan, allows you to heal a party member to full hp, without using any magic. Likewise, Treatment and Revive are great ones too.