I know someone who makes his living with rebuilding battery packs. A standart job is affordable.
When I also give him the charger with the dead battery pack, he is able to make the optimum selection for the "new" set of batteries.
In most cases the new pack will outperform the previous one by hours.
I would say yes, there is a strong demand. Speaking of consumer goods, the market of devices with non-replaceable batteries is growing. "They" don't want you to prolong the life circle of their by definition bad designs. You will be confronted with warranty issues ect.
But more and more people are not willing to throw something away because of dead cell packs.