Just a few quick notes:
1. I thought P2 (DH?) just got an Amex Gold that'll make him 5/24 in less than two months (unless I got my count wrong)?
2. If P2's 4/24 includes the new Amex Gold, then:
a. The CIP would not add to P2's */24 count. The CIP has a $5k MSR, which could keep you busy for a month or two.
b. If P2 applies for the SPG Lux 125k offer in early December, that's another $5k MSR. Amex will not report the SPG Lux until the close of the second monthly statement. While the SPG Lux will add to P2's */24 count, it probably won't show up and make him 5/24 until early February 2019.
c. Now P2 is at 5/24, but with the store card dropping off just a month or two later and bringing him back down to 4/24 in March/April 2019. This could open up the possibility of another one of Chase's 5/24-rule cards.
d. P2 could bide his time at 5/24, waiting to drop back down to 4/24, with an Amex business card (subject to whatever has a best offer at the time) or with P1 (you) taking your turn at a new card, and then when he's back at 4/24, could go for the CIC for 50k UR, if that offer is still available. You mentioned P2 possibly downgrading his CIP to CIC. Downgrading will save you another annual fee, but won't get you another signup bonus. Applying for the CIC directly will get you a signup bonus, and you can just close the CIP if you want when its year is up (or product change that to a CIU).
e. Then get the Chase Hyatt sometime over 5/24.
A few more thoughts.
1. In planning out your cards, look at it as a roadmap with enough flexibility for detours. New cards come out, other cards are discontinued, signup offers go up to historical highs, and drop back down again.
2. Your plan for P2 assumes certain offers will remain available. For example, the Hilton Aspire is up to 150k Hilton Honors points, but not too long ago it was offering only 100k and will probably drop back down to 100k at some point. When you're ready to apply, the 150k offer may not be available. And because Amex welcome offers are generally once per lifetime, you'll want to apply only when the offer is at or near its historical best. Similarly, I've seen at least one DP recently where someone said they called in for the Biz Plat offer and was told the 100k MR offer wasn't available, only a 75k MR/$20k MSR offer was available (I don't know if they called into some general call center, or a direct line into the Phoenix call center that was giving out the 100k MR offers). If these cards aren't available with their historical high offers,
what then? Keep an eye out for alternatives that fit into your overall strategy.
3. I see P2 is missing the SPG Personal card, which I mentioned is rumored to be discontinued in early 2019. If P2 goes for the SPG Lux and earns those 125k Marriott points, what then? That's 2-3 award nights at a decent to nice Starriott hotel. If you'd like to build your Marriott points stash, think about going all in with the SPG Personal before it's discontinued, and the SPG Biz (as long as the offer is at or about 100k Marriott points). The SPG Biz will not add to P2's */24 count and will keep you guys busy for a while with its $5k MSR. The SPG Personal will add to P2's */24 count, but again Amex will typically take about 2 months to report the opening of this new account, so if you have any business with Chase you can work that delay in reporting into your plans.