I have been asked by multiple people to include pickups on the map. The way I went about this was to implement a drop on kill system for the enemies. Meaning when you kill an enemy there is now a chance it will drop an item that will permanently upgrade a stat for one of your units.
On pick up the item will take a look at the "leveling stats" for all of your living units and then apply the stat increase. As mentioned it will prioritize units with matching "leveling stats", however if one is not found it will randomly assign it to one of your units.
As per usual, please feel free to give me any feedback on the new system.
Notes:
The text descriptions for the new pick up are not as perfect as I would like and I will be working on fixing that in a future update.
If you are confused about what a leveling stat is, please check out the tutorial and be sure to Middle mouse click/ press X on your units to see their unit info.