Okay, I manually went into last_setup.xml and set it back to standard game. Turns out that the thing still crashes when I try to select my mod. Did some renaming of mod files and it turns out that the crash only occurs when the changed traits.xml is present.
As for the log files, the crash occurs in between loading colours and the shipset icons. Not at traits.xml. What gives?
EDIT: Okay, going one-by-one over the added traits, this was the one that borked it up:
<trait id="greenpeace" name="Environmentalism" desc="Mining rate decreased to 66%, Ore consumption decreased to 40%." flavor="Past experiences with climate change and disasters caused by excessive mining have caused your people to become conservative resource users. Ore usage is decreased, but so is mining rate." cost="-1"> Before you ask, I've already added the conflict ids in eusocial and capitalism and edited Economy.as appropriately. What's going on?
<conflict id="eusocial" /> <conflict id="capitalism" />
<hook type="alter" func="Traits::increaseMiningRate" arg0="0.66" />
<tag id="green_mining" /> <!-- Implemented in Economy.as -->