The vanilla inserters have a 180º turn rate that makes them transfer 12 items each second, it takes 0.5s per 90º. With bob's adjustable inserters, we can shrink the transfer time by changing the angle that the inserter operates, so the inserter itself will have the same turn ratio but since the angle that its taking items from and the angle its inserting items into are very small, it speeds up the inserter.
On an horizontal line, the inserter takes items from left to right or right to left and that grab, move, drop process takes 1s on a stack inserter, so its 1s/180º. Bob's express inserter have a base speed of 0.5s/180º.
Express Loaders can move 40 items/s but they are slower than the express inserters with full research, if you have a 90º express inserter with 12 stack bonus, it'll transfter items in 0.25s, which is 48 items/s, faster than the loader. Plus the loader transfers items per tick, so they're UPS unfriendly.
I thought the speed of the transfer would be like Factorissimo2 chests, where the content would be fully transferred, half transferred every set ammount of ticks. For example, a balanced chest every 30 ticks would transfer half the items in the chest inside the factory to the chest outside the factory, until both are even, there's also the option to transfer all, that's how I imagined your chests would behave. By the looks of the entity, the inserter would have a 0º angle picking items and dropping them on the same direction its taking items from, but since its 1 tile apart, you consider 180º speed, so its still 12 items/s. This transfer rate could be faster, with 12 stack bonuses make the inserter to have a base stack of 28 so the chest transfer 40 items/s which is a blue belt worth, and if bobmods is present you change it to 68 so its 80 items/s same as green belt.
All chests should have that feature, but in their own special way, like requester chests would have inserters taking from the chest and dropping on the machines, it would be inside-out direction. Passive Providers and Active Providers would be outside-in, they would take items from the machine and drop them into the chest.
Storage chests wouldn't be necessary to have, but for consistency sake you could make them just like red and purple ones.
You could also make the chests multidirectional meaning if we put one steel chest on each side of your chest, it could be able to transfer items from itself to the surrounding chests or machines. if you also make it angled, we could have 4 machines connected with the same chest in a X formation being fed by it.