Uploading now. It'll take a bit, I'll edit the post with the link when done.
E: https://drive.google.com/open?id=0B4W9L0RBmcddOXNIeC1xWktBblU Here's the mod folder. FWIW, I have a smaller Nex game going with slightly less mods that just did the same CTD. I'll upload that save too if you like.
E2: Actually, here: https://drive.google.com/open?id=0B4W9L0RBmcddRWUyZ0hoUHdLT0E This is the save I mentioned in the first edit. Something I did notice that might be contributing to the crash is that there's a pirate base very close to some non-pirate markets, and so many fights have broken out that tons and tons of scavenger fleets keep spawning.
I don't think it has anything to do with the pirates or scavengers or fights. I did a couple of new campaigns where immediately upon starting, I went to the planet I started at, I spent like 10 minutes setting up my loadout and doing a simulator battle, I bought some crew/supplies/fuel, then I tried to save and it crashed.
After others mentioned it, I did some testing with video card memory and it does seem to be related to that. I use MSI Afterburner to monitor my video card memory. My video card has about 2 GB of memory. When I start a campaign where it uses over 2 GB, then shortly after starting the campaign it crashes during saving. If it uses less than 2 GB, then it seems to work fine. The way I get it to 2 GB is by launching tons of mods. I tried enabling/disabling different combination of mods and it doesn't seem to be related to any particular mod.
From my testing it doesn't seem to matter what mods you use or what you do in game, you just need to get it (close) to the limit of your video card memory.
The best workaround that I've found so far is to disable the GraphicsLib shaders (in the mod's ini file). That saves about 500 MB and then you can still use tons of mods.
EDIT: I wasn't able to come up with a combination of mods where I can get close to the limit of my video card memory and have GraphicsLib disabled. So, I couldn't rule out that the problem isn't caused by that mod. It would be ideal if somebody with less video card memory (like 1 GB) could do a test without that particular mod, to see if that mod is to blame or not - ie. load up so many mods that you hit the video card memory limit, but do not run GraphicsLib, start a new campaign, then play for about 30 minutes and see if it crashes at some point during saving.
EDIT2: Here are the mods I used:
http://www.mediafire.com/file/rlxjdclkcwvrrdg/mods.rarAlso, I'm now a few hours into a new campaign with the GraphicsLib shaders turned off and there are no more problems.