Coring is the only thing besides stability that I use admin points for. And I only bother to go to +1 stability for the most part, anything more is for when I'm too far ahead to upgrade due to my pool. Administrative idea groups are neigh-useless and I make sure to fabricate claims on provinces I'm taking before I go to war, so the costs were always >50 [sometimes even down to 10's]. I made it so even with claims it costs me about 100 and I can still core-conquest on a whim much of the time.
This is because even without !!Lucky!! rulers not building infrastructure makes it so you can get incredibly far ahead in tech with almost no effort. So, do you go ahead and save past your cap or continue to blob [to fight the unrealistically-worldwide-growing coalitions]? Gold is nearly useless in this game; and military buildings only use military points [instead of 25% 25% 50% like I think it should, to represent the building, negotiation with locals, etc].
On annexing: I'm thinking of upping the costs of individual province requests in war negotiation, to prevent you from snagging all the best tax-producing provinces with a 'Conquer x' [where x is a backwater 1-base tax province] due to a mission giving you a claim out of thin air.
I'm thinking it should be atleast 3 times the current cost. 200 per province/200 to annex. 100 to force vassalization and 50 for trade power transfer.
Might keep people from going to war all the damn time if they can't afford to come to peace.
On that note; I'm fiddling with missions and going to see if there's real ones, even flavor ones, hidden beneath the 'Conquer x' ones that appear all the damn time. I'm tired of the only missions appearing being Conquer/Savethepeopleof That [the only motivation to taking these missions is the fact that it auto-creates claims for you, which makes world conquest invariably easy if you're already in a strong position to begin with, unless you think +5 prestige (one battle's worth) is the motivator to choose these..] and Build Fort.
I'm also starting to become severely against the 'annex vassal' mechanic. You can sell a 'vassal' [someone you create out of thin air directly after signing peace with..] provinces, buy a Diplomatic Reputation+5 adviser, and annex the whole thing, with free cores, in less than five years. That doesn't seem right. There's no *Force stop annexation* casus belli, so AI will not attempt to stop you from blobbing in this way, unless I've missed it because no one will lift a finger to stop such things.
I seem to do just great with the constant stream of free claims given by missions and quick core conversions. Only thing that takes too long in my opinion is religious conversion, due to the wonky mechanics behind it. Either buy the missionary +2 adviser, buff it with events/decision/piety cheese [Piety makes Muslim nations incredibly unbalanced for reasons I won't go into now], or watch your missionaries simply never accomplish anything. Ugh. I'd prefer the 2% chance a month to taking 111+ months. I'd prefer a flat rate of conversion, something like 5 years to convert then with the modifiers taken into account. But nope.
Oh. And I made it so full military maintenance only adds 1.5 morale to the max. To represent that it should be baseline morale, not make up a majority of your discipline. Turns those military tech levels into something more than a 'bolting a spear onto a bulldozer' kind of thing. Tech levels should represent your military coming into discipline, not your damn maintenance slider. The slider is still incredibly important early-game, though.