It's a pain to solder vias with wire from one side of a PCB to the other, and if the vias are under an SMD IC then it makes soldering the IC tricky.
Different methods I have found or dreamt up are maybe possible:
1. Put wire through and solder it. This is easy and thevobvious way but has problems outlined above.
2. Use proprietary conductive epoxy paste in the hole. There's a commercial system that does this and it seems to work. It looks a bit messy and I'm not sure of the cost at the moment.
3. Put wire in the hole (wire that is thick enough to not fall out) and then cut it to a small distance from the surfaces. Then use a press to compress the wires and form a small rivet with very flat heads. This should then fit under the ICs. I'm not sure how well the rivet would handle age and oxidantion of the copper. Would it have conduction problems?
4. Use PCB pins. these are tapered pins that you put in the hole and snap off then solder on both sides. Problems are that they protrude above the surface like wire. they also don't seem to be made any more.
5. Use test pins. Similar to 4., but they are still made and sold.
6. Use small 0.8mm copper rivets.
7. Use a 3D printer to fill the via holes by printing conductive copper into the hole. I like this idea as it means that the hole drilling gcode or gerber file can be used to position the 3D printer and all the holes can be filled automatically. Problems include how well the plastic will fill the holes and how well the conduction will work. Conductive plastics for 3D printing are also not that conductive and it looks like a via would end up as around 50-150R, which is maybe usable, but care would be needed when placing them in a circuit.
I'm still investigating...