Memoir 44 base game + armies storage

You can fit your base game (except card stands), and the three army expansions (Pacific Theather, Western Front, Mediterranean Front).

Some rubber bands for the tile storage, terrain features tokens and deck is recommended. I cross the rubber bands on the card deck so they don't apply too much pressure on one side. Some small baggies for the tokens are also handy.

I found that these were the expansions I used the most and what I need to carry around.

In the future I'll be designing boxes to fit the Terrain Pack, Winter Wars, Winter/Desert Board, Operation Overlord and New Flight Plan in the New Flight Plan box. Don't hold your breath though, it may take a while till I find the inspiration.

Walls are 1.6mm wide 
Floors are 1.6mm tall
You can print the boxes and trays with 0 (zero) floors, so your slicer just prints the infill of the bottom layers and you save material. Haven't tried on the tile holder.

Terrain tile holder made by: https://www.thingiverse.com/thing:3372809