I'm not suggesting that it's bad to come up with new ideas. My point was more that there are a lot of normal 5e things that aren't implemented yet (but should be) that might cover some of the things that you're talking about. The two examples you gave both relied on spellcasters - if you want to find a way to make melee fighters more interesting on their own, it shouldn't involve spells.
I would be looking for more opportunities to give melee fighters to work together without the need for any spells. Make an interesting flanking rule. Start putting the help action to use. Let one character trip an enemy while the other shoves them over. Put grappling into the game. Let your musclebound fighter throw your halfling rogue up to that catwalk that neither of them would be able to reach on their own.
