Thank you for the installation tutorial ! Well, after a few years of FSX tweaking, what you describe is a nice little walk in the park!
I am wondering if changing the folder name back to EECH is really required after all installations are done. Wouldn’t creating two separate shortcuts pointing to each 1.16 or 1.15.4 exe files be enough? I’m interested in your feedback.
I am not really interested in the Mi-28, so I think I will not buy EEACH and install the game this way :

EECH 1.16.0 :
- install EECH from GOG
- install eech-allmods-1.16.0FIX1-installer
EECH 1.15.4 (because I want to have a try at clickable cockpits, dual Hind cockpit and advanced Apache avionics)
- install EECH from GOG
- install 1.15.0+2+4
o install eech-allmods-1.15.0.exe
o install eech-maps-1.15.0.exe
o install eech-terrain-1.15.0.exe
o install eech-smoke-1.14.0.exe
o install eech_1150to1152.exe
o install eech_1150to1152fix5.exe
o install oalinst.exe
o install eech-CC_0.3.exe

Is this the correct way or have I missed something?

"We warned you, but you just wouldn't listen..."