I'm not sure I follow? that doesn't adress my issue with the lack of guidelines on how to distribute magic items. The game basically lies by saying you don't really need them, but then the game is littered with monsters who resist non-magical damage.
If the issue of "martial PCs who lack magic weapons have problems damaging foes immune or resistant to non-magic weapons" is a primary concern, then I'm not worried about 5e martial:caster problems. That problem looks trivial to solve.
So no, I'm not addressing it? It is like people discussing how to get someone to the moon, and you are bringing up the flavor of bagels that the astronauts prefer in their briefings. I mean, it is a problem that needs solving, but it isn't all that important to the overall issue, nor is it hard to solve.
Magic item distribution is a tool the DM has to control how PCs interact with the world. The scope this permits the DM is large enough to handle almost all imbalance between PC capabilities.
At the low end of optimization, it is true that you probably want most martial PCs to have at least 1 magic weapon by middle of T2, and if you don't creatures immune/resistant to non-magic weapons become harder for martial PCs to deal with.
At the high end of optimization, the ability for the DM to generate custom items and pick which items occur in the game is important. You shouldn't use the PCs wish lists as a source of what items to give them, because the more optimized PCs will tend to have better wish lists as well. Instead, you should seek to provide items useful to the least optimized PCs in the effectiveness realm, and utility items useful to the most optimized PCs.
You can also just punt and use random item generation. This will tend to provide enough magic weapons for most martial PCs by mid T2 to have one if I have seen the math (if not their ideal weapon choice for optimized PCs).
The worst of all worlds is magic item shops (or equivalent, wish lists or whatever), providing a full shopping list of magic items that the Players can pick and choose over for their character's build.