After much testing I created my own way to force Steam and CS do things my way :P and I do it in a specific way to get faster loading times. This was prompted after Harmony 2.0 came out and my loading times almost tripled in some cases.

Yes, it is an involved process at first. It does require a person have all their Non-Harmony, Harmony 1.x and Harmony 2.x mods in separate Steam Workshop collections for easier Unsubbing/Subbing ability. However given that with the multiple people I have worked with, including myself, cut their load times in half I considered it well worth the effort and time it takes up front.

My personal best was from 15 minutes down to 4 minutes with 8.7k assets and 120 mods. The most recent individual I assisted started with a 13 minute load time and was brought down to 4 minutes with 9k assets and 129 mods. So again, quite a bit of up front work, but well worth the time it saves in the long run. I average a "reset" of my mods about once a month but since everything is set up and I maintenance my mods regularly it only takes a few minutes to complete now.

The easiest way to get an idea of how long your loading times are is to check your Loading Screen Mods Asset Report at the very bottom of the report. Do not go by what the screen tells you as that is only how long assets take not total time. The total loading time in LSM is approximately 15 seconds off from the time you click the Load button for your map until yo actually see your map in the game. So precise enough for our purposes of reducing minutes :)

You need to create 3 Steam Workshop Collections. One for Non-Harmony mod, one for Harmony 1.x mods and one for Harmony 2.x mods.

To determine if a mod is Harmony or and which version it is go to the content folder found on your computer. For a default Windows user this will be located here: C:\Program Files (x86)\Steam\steamapps\workshop\content From there you can do a search for the Mod ID number. Mod and asset ID numbers are the numbers found at the end of the mods web address (URL). As example Harmony 2.0's URL is: steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2040656402 so in the content folder of your computer you would search for 2040656402 to find the folder for Harmony 2.0.

Harmony 2.x mods will all have on the CitiesHarmony.API.dll file in their folders.
Harmony 1.x mods will all have the 0Harmony.dll in their file folders.
Non-Harmony mods - yup, you guessed it, have no harmony files :)
Harmony 2.0 is actually a dependency to link Harmony 1.x and Harmony 2.x mods together to reduce conflicts and is not technically a mod so you will see it has both files in it's folder. Please make sure you put it with the Harmony 2.0 mod list however.

Based on this information create your collections. Obviously you can use mine as a reference as well.

Reminder: Your system specs and resources can obviously play a factor on how well this may work for you.

The steps must be followed exactly or I cannot say they will work. I tried many workarounds to avoid a tedious process this was the one that gave me the best results.

1. Unsubscribe all mods from all 3 collection lists
   
2. Temporarily move any local mods out of Local App Data folder
   
3. Load CS to the Main Menu
   
   
4. Check the Content Manager to make sure no mods other than the original base game mods are listed.
   IF you have mods still listed then they need to be put in their proper collection list and unsubbed. After unsubbing any missed mods make sure to RE-enter the Content Manager to ensure they are gone (Steam isn't always cooperative :) )

After all Mods have been unsubbed and/or moved:

1. Clear download cache in Steam settings
   
2. Verify files in Steam
   
   
3. Check to make sure there is not an update in your Tools section (Listed with Games but you may need to checkmark it) for *Steamworks Common Redistributables". If there is, update it, you may not remember but this auto-downloads when you originally get CS and often times other games that use the workshop as well. - Verifying files should take care of this but stranger things have happened :)
   
   
4. Load CS to Main Menu only
   
5. Exit to desktop
   
   
6. Add back in any NON-Harmony mods you may have had locally
   
7. Sub to all NON-Harmony mods WAIT FOR STEAM TO DOWNLOAD
   
8. After Steam is done downloading, remove the download info (this is just to help keep track for the next ones :) in case you get side tracked you know if something has or has not worked right).
   
9. Load CS to Main Menu only
   
10. Exit to desktop
    
    
    
11. Add back in any Harmony 1.x mods you may have had locally
    
12. Sub to all Harmony 1.x mods list WAIT FOR STEAM TO DOWNLOAD
    
13. After Steam is done downloading, remove the download info
    
14. Load CS to Main Menu only
    
15. Exit to desktop
    
    
16. Add back in any Harmony 2.x mods you may have had locally
    
17. Sub to all Harmony 2.x mods list WAIT FOR STEAM TO DOWNLOAD
    
18. After Steam is done downloading, remove the download info
    
19. Load CS to Main Menu only
    
20. Exit to desktop - YES, YOU NEED TO! Do not just go straight and launch!

Yes, it is a bunch of "rinse and repeat" at the end but I wrote it out so nothing could be considered skippable :)
That is it! Now launch a map and do a comparison to see if it helped you reduce your times at all from your original LSM report to the new one.

Hope it helps!