Tokyo is on the far side of Honshu, way better protected than the waters around Guam.
Tokyo is still far closer to the Chinese coast, and the number of missiles available increases exponentially as you get closer.
And guess what - that's how logistis work. Goods flow from South China north to Shanghai, then to south on a route to Rotterdam far to the west which requires a last leg of going eastward, then they are moved from there to destinations southwest of Rotterdam.
Hubs are about logistics efficiency, not about shortest routes. Few logistics schemes use direct connections (that is about shortest routes).
There are two concerns for supplying Guam and the NMI. The first is food and other necessities for 250,000 people, and the second is military equipment. Right now, most of the civilian logistics in Guam come from Japan, but everything that the US military in Guam needs would come from the United States. Trying to send all of those ships through the Philippine Sea to get to Guam makes no sense when the approach could come from the east.
Unlike you, I'm not ruling out a historically well-known scenario (oceanic convoys for protection against subs) for the future.
Moreover, the thread here is literally about that. The Flower corvette was an oceanic anti-submarine escort, the thread started with asking about a cheap small ASW ship (on a civilian hull).
Even if you are going to assume that convoys with ASW escorts would exist, there is no civilian hull that can actually escort them. An ASW escort based on a civilian PSV/OSV or trawler is going to be much slower than a container ship and have much less range, so it could only be used on barrier operations. To escort a convoy of container ships with a civilian hull design, you would need something like a 20,000 ton container ship with ASW helicopters (set up like Atlantic Conveyor) just to keep up. Any towed arrays or hull-mounted sonars would be entirely out of the question.
Any GIUK cordon ship would require much longer-ranged ASW protection than needed to keep sub torpedoes from sinking escorted ships. GIUK patrol requires survivability like a AAW picket ship due to the air threat.
The best surface option for barrier operations would be a combination of frigates and USVs. A corvette like what you propose would be both too lightly equipped and too expensive.
South China Sea, East China Sea, Yellow Sea, Sea of Japan...
All in the Western Pacific. These areas would have such a severe air and missile threat that moving shipping through would be unsurvivable before you even consider submarines. You could think about moving CSGs into the Philippine Sea, but that would be risky with the number of DF-21s and H-6s the Chinese have, and anything less defended would be even more vulnerable.
Mediterranean Sea, Baltic Sea, potentially the Black Sea...
Modern SSKs are a very different threat profile compared to U-boats. In WWII, the U-boats could operate in the open Atlantic because they could run a 20 knots on the surface, but doing that would be suicide today. Kilos would have to operate on batteries and snorkels in chokepoints or coastal areas, which makes dealing with them more a matter of hunting in their operating areas and routing cargo ships other ways. The open-ocean U-boat threat is more similar to what we could see from SSNs because modern SSKs have, for the most part, had to sacrifice their range and speed for survivability compared to WWII-era submarines.
The difference is that Hawaii-Tokyo can be done entirely in deep ocean, while Hawaii-Guam is dodging through dozens of island groups that would be really good places to ambush a convoy or place mines for a convoy to run into.
The Hawaii - Tokyo route runs all the way down the Izu-Bonin-Mariana arc, which does have a lot of islands. While there are a lot of seamounts between Hawaii and Guam, there the only place they come above water is Wake Island and the vast majority are guyots with tops no higher than 3,000 to 4,000 feet below the surface. Detouring through the Marshall Islands would add 500 miles to the transit.
ASW sensor wise, you need a minimum of two sonars just to do the job. either a hull sonar or a surface towed array, and a VDS. The hull sonar is listening for subs doing a periscope approach (which is still basically required for torpedo attacks on surface ships), and the VDS is listening for subs going below 300ft and going fast to reposition. For ASW weapons, you're going to want UAV or helo-delivered lightweight torpedoes. LWT launchers on the ship itself are not much more than giving the crew a feeling of fighting back, so could be skipped if they take up too much space.
You're also going to need self-defense AA. For the Brits, a CAMM mushroom farm and whichever radar can cheaply provide the necessary tracking. For the US, a couple blocks of ESSM in vertical launchers plus RIM116 and Sea Giraffe or TRS-4D (if those can talk to ESSMs, else we gotta step up to 3x9RMA SPY6)
And now we're suddenly up to pretty expensive ships because they have ~100mil worth of sensors and weapons on them.
For the bare minimum capability.
A warship with enough machinery and fuel to keep up with a convoy of container ships over long ranges is going to be large enough to handle a standoff ASW system like a helicopter and expensive enough to be worth defending with SAMs.
Submarine-launched UAVs could be another target for convoy air defenses. If a submarine launches a UAV, it could communicate with a floating communications relay either via a fiber-optic line or acoustic communications while remaining under the thermocline. That could eliminate the need to come to periscope depth to identify sierras before a torpedo attack, while electric swim-out torpedoes could make it easier and safer to fire torpedoes while staying deep.
The fundamental difference between the threat environment that the Flower class corvettes saw in the Battle of the Atlantic and what we have today in the North Atlantic and Western Pacific is the air threat, both land-based ballistic missiles and anti-shipping bombers and submarine-launched anti-ship cruise and ballistic missiles.
