Fixing the problem with coins being split into single-coin piles and never recombined, would probably also fix the problem with used crossbow bolts never being restacked. Though that problem would be difficult, what with not only the difference in bolt quality, but maker and ornamentations as well.
Restacking of crossbow bolts is irrelevant, since the dwarves can put multiple stacks into their quiver now. This is a huge step forward from 40d, where they could only carry ONE stack of bolts in their hand, or one stack in their hand and one in their quiver. Granted, stacks of bone bolts were bigger than 5 back then, but still....
The issue with coins was just another symptom of the general issue of hauling and inventory. Dwarves can only haul one item at a time, and they don't use their hands to do so. They seem to have an infinitely large Hauling Pouch as part of their anatomy. When someone brews a stack of prickle berries and generates 8 seeds,
8 dwarves have to come and haul the seeds, one seed per dwarf. It's faintly ridiculous, and I'm sure Toady plans to fix it at some point, but it's obviously low priority.
The fix for coins will probably be something like the fix with quivers -- you can put multiple stacks of bolts into a quiver now, and some day in the future, I'm sure you'll be able to carry multiple coins of various types in a pocket, wallet, coinpurse, whatever.
Likewise, I'm sure some day a dwarf will be able to pick up more than one seed, and carry them all to the seed stockpile at one time, possibly using a basket, or a pocket, or just bare hands....