The original Scimitar of Speed is among the Magic Weapons listed in the DMG:
Scimitar of Speed
requires attunement, very rare
- You gain a +2 bonus to attack and damage rolls made with this magic weapon.
- In addition, you can make one attack with it as a bonus action on each of your turns.
Being able to use your bonus action for a melee weapon attack regardless of any other actions on that turn can be very useful for melee casters. Hence, I see the second bullet point as the main feature of this weapon, while the bonus to attack and damage rolls is nice but nothing unique.
The following weaker variant trades the bonus to attack and damage rolls for a lower rarity level.
Scimitar of Speed (weaker variant)
requires attunement, rare
- You can make one attack with this magic weapon as a bonus action on each of your turns.
Is this variant balanced? If not, what would be the appropriate rarity level to fix this?