Now that the disaster was over, I could do some expanding. Except everyone except me was on mil tech 4 or 5, while I was still at 3, so maybe that should wait a bit.
New 1.31 bugs
So now we get into another issue with 1.31. Majapahit is supposed to create vast empire of tributaries, and that used to work, except at one point they changed the code and you can only create tributaries you neighbour by land. Not by sea zone like with everything else (fabricating claims etc.). Oh and they removed most straits in the regions. Do they even have QA?
Anyway, I conquered myself a few provinces, and that let me ask 7 countries to be my tributaries. I have unique mission that converts all tributaries into vassals.
So why not get myself 7 new vassals this way, getting me massively over relationship limit? Well mostly because more bugs. New vassals get modifier that makes them very loyal - but that doesn't apply to my existing vassals, who look at relative strength including those new superloyal vassals. There's same bug with having HRE vassals swarm (who are correctly loyal) and some non-HRE vassals (who incorrectly look at HRE vassals swarm and decide you're too weak). So that's a third issue I didn't discover in testing.
No big deal, I'll just take my time and annex 3 existing vassals first. If I knew, I wouldn't have make vassals. In the meantime some more conquering.
Conquest plan
So basically I wanted to either conquer everyone south of Ayutthaya, or turn them into a tributary (as they'd then be a free vassal).
As nobody will accept being a tributary unless I neighbour them, that means I needed to conquer myself a lot of neighbouring. And there were also some OPMs I probably shouldn't have bothered tributarizing, as OPM vassals are a waste of vassal slot - even if I get 6 base, +2 strong duchies, +1 Majapahit mission.
Another thing is that I'll need to annex them eventually, so this is really asking for some idea group that gives diplomatic reputation, or extra diplo slots, or annexation cost reduction. Meanwhile I'd really much rather take religious or exploration. Well, can't have everything.
Enforce Loyalty
So after conquering my way around, I clicked the Enforce Loyalty mission button, converting all my tributaries into vassals. Now I control the whole islands except for Brunei and OPM Siak.
I annexed my old vassal Makasar, and my two other old vassals Tidore and Malacca got bribed into behaving.
So far I got up to 433 dev and 275 vassal dev, and monthly income of 39, making me 4th Great Power after Ming, France, and Ottomans.
My capital alone is 81dev, weirdly at 35/31/15, I guess that's a quirk of how concentrate development works (if it's not divisible by 3, it goes in order: tax, production, manpower).
And that's it!
Normally I'd play longer, but this campaign had zero challenge, and it's only going to get less challenging.
Concentrate development is ridiculously overpowered, and I didn't even abuse it, just pressed when it was easy.
Before the 1.31 patch most countries tried to build army up to force limit. This time they mostly don't, and it's common to have a country with 1k or 2k troops. Also everyone drills nonstop, even when I'm standing in next province at their border, so I can wipe out any army at any time.
I guess naval combat was the most challenging of it all, as I was usually seriously outnumbered, and with some straits removed, and hostile landing time increased, it was actually important to winning wars.
I can see how the disaster would destroy Majapahit AI every time, and if you're unprepared (or fall for the Muslim trader event - it's a trap, you must say no) it might be a bit of a challenge, but really, without simultaneous pressure by some foreign power it just didn't matter.
Maybe Khmer disaster is actually worse, as Khmer might need to face Ayutthaya and Lan Xang in the middle of its disaster, but AI Khmer is usually doing a lot better than AI Majapahit so maybe not.
To be honest, I'd still recommend playing 1.30 patch. Or some other game.