On their own it won't be enough to deal with belt problems
I find that hard to believe. A blue belt with size 4 stacking will move 160 items/sec, with 80 items per lane. That's a lot of items!
I think you misunderstood what I meant with that. I didn't write that stack belts aren't capable of dealing with throughput problems. Actually I am pretty sure for bulk transfer it would be rather nice.
What I meant instead was that I think that in unison with some of the inserter problems it won't be enough to just increase the throughput, which I count towards the belt problems, hence the "on their own it won't be enough", or at least not for all applications, as described further below.
inventory-to-belt transfer speed of Inserters are also a main source of the limitations at hand even with Stack Inserters
I also find this hard to believe. A flat belt can be saturated with 3 upgraded fast inserters per lane. Multiplying the belt capacity and inserter capacity by 4 (inserter 3 => stack inserter 12) leaves these values the same. It's not a big deal to use 6 stack inserters to super saturate a belt. That's one side of a train unloading station, with each train car saturating a super belt.
The small question is if such high capacity can feed a module/beacon setup. I think they can. The big question is if it players will use those stronger belts in their builds. That's a bit too difficult for me to know!
How do you plan to put all the necessary inserters in between beaconized setups for high volume recipes like electronic circuits?
Electronic Circuits are currently already rather hardcore to try with belts between beacons. I tried, and couldn't get any setup to work reliable without serious machine stalling problems due to inserters being too slow or interfering with one another due to accessing the same belt. Inserters interfering with one another becomes actually a problem even with other recipes as well if they need a lot of ingredients, like for example Processing units, especially when two nearby inserters try to grab electronic circuits from the same belt lane forcing one of the stack inserters to jump back and forth between the near and the far side lane, further delaying the input due to how every time the inserter has to re-adjust the arm position costing additional time.
Even with normal recipe requirements for electronic circuits etc I already find it stressful to do it with Bots. Even with bots I already need 3 Stack Inserters (1 for Iron Plates, 2 for Copper Cables) with their inventory-to-inventory bonus to keep up with the input of Iron Plates and Copper cables and a 4th one for the circuit output so that the assembler doesn't start stalling. But it is do-able and I am using such a setup currently in my normal recipe difficulty games.
On expensive mode it is almost... impossible even with bots because of how you only have space for 6 inserters around the machine at best between beacons... and somewhere you have to get power from as well so a powerpole would probably also be somewhere, except if you use substations, but they are even more bulky and almost don't fit in without sacrificing some beacons or machines. So it is hard at the limit of what is possible.
So how do you do it with belts where the inserters are even slower and more limiting?
How do you think a stack belt with for example 4 items per stack would keep up with that if a stack inserter requires to wait for at least 3 stacks (if fully compressed) to come by before it can swing to achieve what a single Stack inserter can do from logistic chest-to-machine without having to wait? So you probably need more inserters to access the stack belt in parallel to avoid machine stalling... again, leading to all kinds of space problems as described above... hence why I would probably say screw that and go for bots... again.
So what that means for me is that some adjustments to the Inserters might be necessary as well, or otherwise the belt stack wouldn't solve all problems for why I abandon belts.
I mean on your slow crafting speed / low-ingredient / low-demand recipes Inserters don't matter anyway because even if it is a beaconized setup the inserters are faster at loading/unloading than the recipe can craft and require ingredients or output items. But on those recipes you mostly don't even need stack belts anyway because you only ever have maybe 1 belt or so of them and it doesn't even need to be an express belt.
Ore/Plates recipes are the most reasonable sweet-spot though... average crafting times and resource requirements, hence no inserter problems. Yet you still need a ton of ore and plates, hence where stack belts would shine most.