The FSPort is just an example, let's not mention that project all the time and make it look like the cause of a problem.
Here's a possible scenario. Watsisname and/or any other creates a new set of nebulae, planets, skyboxes, etc., which for a variety of reasons are not included in the MVPs. They're not popular enough, the MVPs will come out in a few months time or more, said bitmaps do not fully match the style of FreeSpace, whatever.
The set is big in terms of dimensions, let's say many dozen mbs.
Now, imagine that the pack is successful enough to become common in fan-made campaigns, but still doesn't qualify as something you'd add to the MVPs. How would you handle the situation? Would you simply allow each campaign design to add all those files to their own modpacks and release them?