So I was thinking after seeing a picture of an elf bard, why shouldn't elves get a buff to it.
When we analyze elves they've always been interconnected with music and magic, so my suggestion is simple.
Elven and Half-elven bards should be able to wear medium armor without any penalty without any penalty to spell casting.
Elven and Half-elven wizard and sorcerers should be able to wear light armor without any penalty to spell casting.