stacking comes from the idea of trying to save space. Like as it stands now if I have 99 logs, I"m better off holding onto those 99 logs because by converting them into planks or lumber I'll be losing space. In the same instance if you have 99 mats for ingredients for food and make it you have 12 a space which would become like 9 inventory slots taken up, even if you are synthing a food that uses 8 ingredients and you use them all up you won't be saving space since they don't stack.

I think what they should consider for items is perhaps this tier of cap on inventory items.

For gathered items I would propose keeping that at 99
As for things like planks and thread I believe it should be a 255-500 cap
Weapons of course single
Food should be 99 just because of mass production and accessibility of actually being able to store it properly.

However, if they don't want to do that then I think a nice balance woul dbe perhaps being given the option to buy a "gather specific" bag that can stack more of said item per inv slot to at least help those that gather. As a botanist even when I focus purely on gathering logs/branches/feathers, my inv is still cluttered after logging within the same area.

If that doesn't sound feesible then another suggestion I have is perhaps having it so something like
log
log +1
log +2
log +3

can instead be
Name:00:+1:+2:+3:Cap
Log:::23:05:07:10::45/99

I don't think it would be hard to implement the above when people choose what HQ they want to use they can just hover over the item, then click on the 23, 5, 7 or 10. and they'll use that HQ of the mat or perhaps just the NQ.

If the community reps can shed any light on how they possibly plan to alleviate the issues with inventory space even now, I hope it's not just increasing inv cap, since you can only go so far with that. I think it would be better to try an implement something that I suggested cause at least then 10 materials that have a variable of 4 quality would take up 10 spaces instead of 40.