Since I just sparked this Idea I write it down without checking around first.
I remember the great and wise Toady One once wrote on the topic of restacking in some voting poll that there are problems with quality, material and some other stuff concerning bolts and arrows which prevents him from putting stacks of bolts together again.
I remember him talking about virtual containers or data loss.
My Idea is to use Quiver as actual containers.
If this is old news, just stop reading, tell me so and I will shut up, if the idea is actual worth reading go on
If you use them like Barrels and Seed-bags the dwarfs could collect the bolts or arrows and put them into an empty or not completely filled Quiver. This way all the ammos information is kept, but one dwarf can still take a large number of stacks with him.
The Quiver would the be called Arrow Quiver or Bolt Quiver and put away in an ammo stockpile. There it can be stacked in bins like seed bags in barrels.
I don't know how seeds are handled, if there are no empty bags, but I suggest if there are not enough quivers the ammo should just be put in bins like it is now.
I suggest a maximum of 100 bolts to fit into an quiver ( since with size 20 creatures, this is the largest stack possible ) and the same maximum for stacks .. so a dwarf can take 100 single bolt stacks with him.
I understand this will give quite a boost to the archers, but I want to avoid the problem large stacks of prepared meals have.
For sorting I suggest two things.
First make an option like the mixed food barrels .. every bolt goes into a quiver, no matter whats it made of or they are sorted by combat bolts ( metal ) and training bolts ( bone and wood )
Second : Custom Stockpiles.
I hope this could work in a way, that as much code as possible can be reused without making big changes. I think this would make the community really happy.