I see sprite sizes more as recommendations than requirements ;) NES games still did this even with all their limitations, mostly by using more than one sprite, with the sword in one sprite and the character in the other... this also let the designers use a different color palette for the sword as a bonus effect. Check out the sword powerup in Kirby's Adventure, for an example of this... but Zelda 1 and Castlevania 1-3 all did this approach as well. (In modern days, you can of course have it all in the same sprite for convenience)