Modifying Bard's Magical Secrets

[PhoenixPhyre]

I'm brainstorming ways to make the way casting classes access their spells feel different from one another. Right now, the only difference is in spell lists.

I've written up a thematic magic revamp (in my signature), but my current focus is on the Bard.

What if, instead of Magical Secrets, they got the following ability:

Harmonic Magic
Beginning at 6th level, you have learned to hear the harmonies of spells as their cast and to mimic them. When you see and hear a spell being cast, you can attempt to fix the harmonies in your mind to reproduce them. The spell must be of a level you can cast. Make an Intelligence check against a DC of 12 + the spell's level (cantrips count as spells of level 0). On a success, you learn the spell and it counts as a Bard spell for you. You can only learn a number of spells equal to your Intelligence modifier this way, although you can sacrifice one learned spell for another.

Lore bards would get something like advantage on the check or a larger number of spells learned that way.

How does that break things? They have to find spell casters, and it's based on an off-stat (and no proficiency, Jack of All Trades applies but you can't get expertise). Underlined things are variables I don't have fixed down right now.

[Fire Tarrasque]

That is... VERY powerful.
Sure, if the bard is alone, it's fine. But if that ability is in place, Int WON'T be a dump stat.
The main problem: There WILL be other spellcasters in the group.
Nuff said.

[PhoenixPhyre]

That is... VERY powerful.
Sure, if the bard is alone, it's fine. But if that ability is in place, Int WON'T be a dump stat.
The main problem: There WILL be other spellcasters in the group.
Nuff said.

What if it's combined with a much more limited "native" spell set or it's limited to just a couple spells (like maybe 1 at 6th, 2 at 10th, 3 at 14th to mimic the current Magical Secrets?)