I noticed that the Planes and Airtanks are still HoI4. My suggestion for them is to convert HoI4 Vehicles to Slimestone Vehicles. This would be a good way to change up the mainstream strategy. (I haven't tried the mod yet. I'll include my experience with it after trying it out.)

Here's an unfinished list of example slimestone vehicles HoM could use. example Slimestone Tanks:
[ul]

• Giant Tank
  
• Barebones Tank by Cubehammster[/ul]
  
  example Slimestone Airplanes:
  [ul]
  
• Fighter Plane. Good for replacing generic HoI4 planes.
  
• passenger airplane
  
• Bomber Plane[/ul]
  
  and example Slimestone Ships: slimestone Ship Slimestone submarines can replace the HoI4 ones (example Slimestone submarine). Slimestone trains exists as well, so they can help substitute any HoI4 trains that can't be represented with Minecarts. HoI4 Trucks as well (example).Of course, slimestone vehicles in Minecraft are not limited to just those; there are far more possible slimestone vehicles, like this griefing machine.
  
  HoI4 Missiles would be converted to Slimestone missiles as well. Here's a list of Slimestone Missiles as an example.
  
  Slimestone vehicles concept could be expanded to add Slimestone researches, mostly about flying machines. A bunch of slimestone vehicles can easily become researches.
  [ul]
  
• Ice Highway Builder be a research that increases construction speed.
  
• this tunnel bore, that improves mining speed, could become a research that improves mining speed.
  
• this auto-quarry increase mining production. (Production and Speed are not the same thing.)[/ul]
  
  But I think some of those contraptions should really be their own vehicles. A better example of an actual research would be this early Missile Factory that multiplies slimestone missile production; based on this tech, a research could be created and named “Basic Missile Factory”. (The more advanced slimeblock printer by Cubehammster, could follow the “Basic Missile Factory” research. named “Slimeblock Printing”)
  
  Alternatively, some slimestone researches could instead be more long term, to unlock certain mechanics. for example, a “Slimestone Safety” group of researches that reduce or accidents. Anyway, the slimestone researches could then be grouped into a Slimestone research field.
  
  Regarding Resources, Slimestone vehicles would cost Slime. Slime would be generated only in Swamp biomes or Slime chunks, could marked by the existence of either Slimeblocks or Slime mobs. If a province is both, then the production rates from either are combined.
  
  I'm going to expand this comment into a better written post. Also I have a feeling that I'm going to be writing about this for a long while, probably until the next day.