I'm experimenting with that now... not entirely sure yet, but it may be the case.
But also, remember that .esm files load high in the load order automatically.
In Phalanx' case, I cannot make it all an .esm because lotsa mods conflict with some of Phalanx' content. I will end up with an .esm and an .esp, is how it looks, for what's in mainfollowermodule now.
If you're editing an external cell and have changed the navmesh, there's something extra you need to do to your navmesh to make it override fallout3.esm's. But me being a newb I don't understand just what that is.
Cool, I can deal with that - I've not had to play with .esm's and was trying intentionally to keep everything for my mod in a .esp to avoid conflicts.
Fortunately I have not modified any of the Fallout3 game whatsoever (and will only do so as the last step to add the entry-way) - I created my own world space. Thus far I've done a 10 x 6 cell exterior Business District (its a lead-up area to my main area), and I have alot more exterior area that I'm going to be making an Navmeshing. So far I've Navmeshed most of the exterior cells I've created, so hopefully I wont have to change anything with it other than to move it all into a .esm.
My mod will be Very large, but especially in the sense that I'm focusing on level design and making huge, interesting new places to go and explore with several quests and a well-defined theme - light on the coding side (so far). So the impacts to the cells I've made is where my big concern is - I have 5 large interior cells in addition to the exterior one described above. If I seem to be freaking out about this, it's just my over-worry about losing so much work.
Thanks for the testing, I owe you one.
Miax