But making each layout a new level can add up to the final size quite quickly, at least that's what i've experienced before.
By doing this, my game was 3mb with 1 layout level. When I switched to external files for maps, the game was 300kb, with each level being 200kb.
Making each layout a level also creates problems where if you need to change something later, you need to go and change it on each layout (not sure if thats how it works on C2, but I had this problem way back when using MMF2)
I hope C2 soon adds supports external files, like arrays and inis