Allright, so I'll post here what I posted on the other resource (double created?)
Really nice system, it has some issues but you probably can fix it!
Here are some things I noticed!
1 - The main thing I noticed is that you use dummy units with expiration timer to simulate countdown timers. I used to do it that way too, now I use countdown timers, which I recommend you do to improve performance of your map as of every dummy unit you create (doesn't matter if it dies or is removed) some memory is permanently leaked, you can use a dummy recycler too but I think countdown timers is more recommended.
2 - Another issue is that if I order the unit to harvest from the source it will immeadtly recieve the "Harvesting" buff and also starts the animation, this will happen even if I order the unit with something else in the process (like stop for example), they will begin to mine on the air, not to mention the gold source will be damaged in the process.
3 - If a unit is mining and is ordered to stop or hold position, it won't stop it's animation or the whole mining process.
4 - The value of gold returned vary if the unit is ordered to do something else in the process (sometimes I get 47 gold from a single peon, others I got 135).
5 - You should use a unit indexer to make unit's custom value unique.
I hope you see this as a constructive critic to help improve this project