If you want a time critical strike capability, a SH(s) still has to be launched to carry and fire a hypersonic missile(s). Will the SH(s) be in a holding pattern, waiting for the call to strike? If so, then the proximity to the target provides a benefit. But if not, then the speed and travel of the ship-based hypersonic missile will outpace the sudden launch of a SH and provide a faster reaction time.
Yes and Yes. The idea would be to use the evolving carrier air wing to defeat some of the most well protected targets, by either targeting the A2AD capability, or attacking targets despite of its presence. Idea would be to use the stand in force (mainly F-35C's for the Navy until NGAD begins to show up) and backing that up with a Stand Off force (Growlers and SH's). The advantage of the former is the sensor system, survivability, and the ability to launch cheaper munitions from closer. Limitation is the magazine size and that the navy won't have more than 14 F-35C's in each wing. Even when NGAD shows up, SH will still continue to dominate numerically for at least the next 15 or so years if not longer.
Advantages of the SH and Growler are numbers. They can bring capacity because they constitute majority of the air-wing. Limitations are the inability (and increasingly so) to penetrate sophisticated IADS in the future. Navy's connectivity can help out in that the penetrating force not only attacks targets, but also provides near real time input to allow the stand off force to contribute from afar. There is a reason why the Navy now suddenly wants to add the JASSM-ER on the Rhino for the second half of the life of that platform. JASSM-ER while provides them the SO capability, takes too long to get there and future kill chains may not support that. A quick reaction weapon that has the legs, and the speed can really help here. It will be shorter ranged, and significantly cheaper than what the Navy can hope to put on a surface ship, and it will allow the Navy's air-wing to be a relevant player in the post 2030 fight instead of only having a fraction of the fleet being capable of fighting the high end fight.
If you envision a scenario where we want to defeat a target that we've just found then yes, launching an AC from a carrier, waiting for it to reach its intended launch point, and then launching a 500 mile Mach 5 weapon would be much slower than launching a 2000 km ranged hypersonic weapon from a submarine assuming that the sub or that Zumwalt happens to be at the right place at the right time and with the right weapon. But that isn't the only time-critical / quick response strike that may be needed in the future. A high speed JASSM-ER analogous has extreme merit and there is good reason that the Navy is now following the USAF's HACM in creating a program that gets them that capability. It will be much more affordable to buy than the larger longer ranged hypersonic weapons, or even the TBG systems like the ARRW.
I'd guess that a 500 mile scramjet cruise missile can be had the range of $5 Million per round or roughly half of what the ARRW AUR with about 2x the range is expected to cost. IR-CPS/LRHW in contrast will cost north of $30 Million per round. Lower cost options open up a lot more targets against which you can use these weapons so missions outside of time-critical strike like using one or two HACM's to defeat defended targets that may have required 2-3 times more JASSM rounds. Setting cost equation aside, this now means fewer platforms (armed with HACM/SA) can now hold targets at risk compared to if the only AL-SO option available was the JASSM. That has significant cost imposition on an opponent. The opponent knows that you don't necessarily need to amass a very larger force to make its life a lot more difficult.
IR-CPS / LRHW is not the type of weapon that gets you a very large hypersonic inventory. Its performance, size and cost basically means that it will be produced in the low to mid hundreds at best. ARRW too, with its 1,000 mile range and $10 Million AUR cost is not the type of weapon that will exist in the thousands. Get to half that (half the cost, half the range, but still Mach 5+ speed) and you can get a weapon that you can produce in the thousands. If the AF and Navy plan on fielding an inventory of 10,000+ JASSM/LRASM's, then there is no reason why we can't have an inventory of 2-3K HACM/Screaming Arrow's. That's a major boost for the tactical fleet and even bombers that can get close to about 500 miles of the target. If HACM/SA end up being B-21 IWB compliant then that is really a giant leap in capability which will not be easy to counter. And that frees up the Navy's VLS for other weapons that can support missions where the air wing may not be as well suited. For example, IR prompt strike will be difficult to support using the SH because as you rightly point out you can't have SH's in orbit all the time. For that mission, a $30 Million IR-CPS may well be worth it. But there may be several use cases for an Anti IADS capability, or a quick reaction strike capability that doesn't require a 3,000 km Mach 10+ IR-CPS weapon with its huge price tag. That tactical level of capability is what HACM and Screaming Arrow need to go at.
I don't believe it would be as nearly difficult to accommodate hypersonic weapons on Navy ships as you make it out to be, they don't even have to be internalized. The modular container-esque design philosophy of some of these new weapon systems provides a more plug & play feature that can be enjoyed by all services thanks to the efforts for continued joint integration of systems.
Hope you appreciate that the Navy's only (current) hypersonic weapon is 34.5 inches in diameter, weighs more than 10,000 lbs. and costs upwards of $30 million a pop as per some estimates.
BTW ASALM reached hypersonic speed (Mach 5.4) with a ramjet.
