Let me go ahead and make a disclaimer
1. I fully believe wizards are superior to fighters so I'm not dismissing that at all. I'm on board
2. Resolving problems with the wizard doesn't mean i'm ignoring problems with the fighter.
That should stop about 90% of the concerns I'm getting back about this topic.
You might want to edit the OP with that disclaimer for new posters. Just a suggestion.
My complaint is that level 1 and level 2 damage spells in level 1 and level 2 spell slots are broken BECAUSE cantrips scale. I don't see how giving more spell slots fixes that problem.
Giving more spell slots doesn't fix this problem, removing cantrip scaling damage does.
On removing cantrip scaling - I don't think cantrips are too strong - instead I think level 1 and level 2 damage spells are too weak later. So while this option would make them strictly better than cantrips - it's not fully fixed my problem as the problem is partially that the low level damage spells are flat out too weak later.
So really the issue (sorry if I missed this before) is that at higher levels, first- and second-level spells are no longer effective options compared to scaled cantrips and higher level spells. Right?
Let's look at a concrete example: Burning Hands vs. Fire Bolt.
Burning Hands does 10.5 damage on average. There is a save, of course, but you are also likely to get more than one target. If we consider those to factors to cancel each other out, we can say the expected total damage is 10.5 reasonably.
Firebolt does 5.5 damage average per bolt (up to 4). It requires an attack roll, so we could argue that expected damage is really about 3 points when we factor in typical hit probabilities. Scaling that up for 4 bolts (at 17th level) would be about 12 points, slightly higher than Burning Hands.
Before the final scale-up, Burning Hands does more damage (not a lot, of course).
Looking at your suggestion, I don't think it is OP.
Burning hands RAW 3d6
@level 5: 4d6
@level11: 5d6
@level17: 6d6
Still never as good as Fireball (8d6).
Would Magic Missile simply get another missile with each Tier jump? Seems reasonable.