Or possibly every mob. This would give the feeling that you can pick up your tools from corpses to reutilize them, even if in reality they wouldn't be the same.
Dora feels the community would rather see the tool limit raised globally, but combined with your idea it can make it even better. It's all up to Rory though, and maybe he doesn't even plan on giving it to us... for free. So there's the possibility it becomes a craftable upgrade or more.
If it ever comes out as a such though, it could become a reward for the 'Reach level x' milestone missions. At each milestone you'd get your tool limit raised up to whatever is decided. It could be a small amount each 10 levels, or just two big upgrades for 30 and 50. Or... if Rory wants to venture in that territory... he could lower the base limit and get it increased a little at each milestone.
Let's say you start with a limit of 100 tools. You'd be able to carry that while being an academy student. Graduating from the academy would set this limit to 200, then each milestone after that would grant an extra 40 to your tool limit, up to 400 tools at level 60.
So watchu say? More booms?