I remember how everyone was excited near Ideology release about what modders will do with the system. Either something in my mod list messes with it really hard, or the answer is "barely anything that works". In my two games with Ideology Expanded and Alpha memes i have seen those break:
Party start plain didn't work.
Sweet tooth adds an addiction-like bar, but colonists, like dwarves until last patches, didn't seek out sweets by themselves. Also, chocolate, of all things, refills the bar slower than one can eat it. And i picked this one because in my previous colony i had a hoard of chocolate that nobody has touched in years.
Bushido was broken horribly, but i don't remember how exactly.
Mood buff from trade has no timer and is active even on faction members that just enter the map.
Exalted clergy... Well, probably expecting it to merge leader and priest instead of giving powers of one to another was on me.
Dafuq.
I haven't tried any of those, but the ones I have tried - astrology, healthcare, scrapper, and insectoid supremacy - have all worked fine.
Some other mods that I consider pretty impactful while not changing vanilla too much (in addition to Scriver's, which I largely agree with):
- Suppression - in practice slows down lethality a bit, and makes combat a bit less of a focus fire fest.
- Fluffy Breakdowns - replaces constant component drain with more labor required for maintenance.
- Water Freezes - more dynamic map by season, at least for those maps where it gets cold enough.
- PawnsChooseResearch - a variant of the random research mods floating about; functionally slows down tech progression significantly, which I personally think makes for more interesting choices. But really a matter of personal preference.
- Better Pyromania, Bad Can be Good, and Well Met - all three combined make for a good suite. The first two make the worst traits less frustrating, while the last of the three hides what traits a pawn has until you've had them around for a while. Ultimately makes for a greater variety of pawns and less incentive to vigorously cull potential recruits.
- No One Left Behind, and Enemy Self Preservation - Latter makes it so that enemies no longer fight to the bitter end 100% of the time, instead individually fleeing when above a given pain threshold. Former makes it so that enemies will sometimes try to rescue downed allies once they retreat. Combined definitely reduces the difficulty of raids, but makes them a bit less silly in my opinion. Also can require a bit more initiative to get prisoners post-raid.
- Silent Raids - adds a new variant of raids / manhunter packs that doesn't pause the game or give a pop-pup, i.e. sneak attacks.
- Mass Graves - what it says on the tin. Makes incinerators less of a rush-tech by providing an alternate method of less space-intensive way of dealing with all those dead raiders.
- Allow Tool - a variety of convenience tools for mass-selecting in certain ways, e.g. allowing all the crud dropped from a raid all at once.
- Brr and Phew - colonists act a little more reasonably in addressing cold, heat, toxins, and cabin fever.
- Common Sense - a slew of minor behavioral tweaks such as not clearing snow during a blizzard.
- Everybody Gets One - New production bill conditions based either on # of colonists or having surplus materials. Especially handy for adjusting meal production on the fly as you gain & lose colonists, though it has other uses too.