TL;DR
One sentence to describe your idea with a bit different words than in the subjecterr....
Introduce non-finite enhancements for maximum component bundle quantities
What ?
Add in infinite research that will increase the stack size of items by some amount, for example 10%.So after 2 researches (using the 10% example) each stack of transport belt now stacks to 120 items.
Why ?
While at the start of the game carrying around 800 belt, or 1000 rail is fine, towards the end of the game when you really start building BIG, even with large trains (20+ carriages) you may still have to make multiple trips back to restock the items you are missing. If you could put resources into increasing the amount that you can carry/hold then it means less trips and a larger variety of items carryable at a single time.It would also help immensely with concreting the base as you could carry more concrete.
Honestly, I would be glad if the upgrade only applied to concrete... *mumbles something about concrete*