Um.........it would be difficult. Very difficult. I think there is someone trying to work them all in but it is very difficult.
Stacking across mods is not supported the majority of the time. Some enhancement only mods of the potential to stack but they fall into the same issues unless they are very generic in nature.
The main issues boil down to key game files that are mod specific and to a certain extent hard coded limitations that prevent mods from stacking.
For example: The GalaxyScenarioDef.galaxyScenerioDef contains the wiring that allows a new race to exist in Sins. Like Highlander, "there can be only one". So stacking Maelstrom on top of Sins of the Fallen would overwrite Fallen's GSD.
There are actually several other files like the GSD as well...
Another issue if you could bridge the mods together (like I did previously with DS) is the various hard code limits that impact the game. The 2GB is the biggest example and is why my mod now stacks the way it does so I can add extra races that can be activated/deactivated to avoid the 2GB limit. The other issue that still plagues my mod is certain hard code constraints like the instant 2000 sound file mini-dump. This alone would make it impossible to bridge Maelstrom with Sins of the Fallen.
There are work arounds but all of them require modding and manipulation of the various mods to avoid these limitations.