Well, on the arena front, yes Pechanga Arena holds 13,000 for hockey and is old. It is home of the San Diego Gulls of the AHL (Anaheim's farm team, owned by the Ducks owner).
But the arena problem is true of almost every single location.
The age of Pechanga Arena already has three developers bidding on a new arena/mixed use plans for the location. Looks like they picked a front-runner, but there's still ballot measures and hurdles... and the intended home team of the arena IS a hockey team, just the AHL one.
The city has 3.5 million people, no major sport from October to March; that just lost the Chargers and lost the Clippers decades ago. An NHL team joining the bid to build an arena to replace Pechanga makes sense. You're gonna have a far easier time getting an NHL/NBA arena built than a AHL/G-League arena built, because "big league" sports are immensely more popular. San Diego (and Salt Lake) don't want to be MINOR LEAGUE, they want to be MAJOR LEAGUE.
San Diego probably the most sense of any option, TBH.
Yes, you have the Ducks/Kings 90 miles away, but (unlike the Bay Area with BART), going from SD to ANA/LA for a hockey game is non-existent. If you leave SD at 4 pm for a 7 pm Ducks game, you might miss puck drop. No chance on the Kings unless you leave by 3 pm.
When you look at "Markets" and see #17 San Diego... oh, it's too close to LA/ANA... take note of who #12 is: San Bernandino/Riverside!
They are 56 miles from LA, about half the distance as SD. But they count as a "separate market" because MSAs are about work/live commutes, and no one wants to make that commute!
As for "territorial rights," the Kings/Ducks have none. That's how the Padres exist, and how the San Diego Chargers and San Diego Clippers used to exist.
The Kings and Ducks can vote "no," but if the Coyotes tried to move to San Diego, got the arena deal done for the Pechenga Arena site... the Ducks and Kings would know they're going to lose 30-2.
The only way it DOESN'T make sense is if the SD Arena project is Samueli's arena project. If the Midway Rising thing is HIS real estate deal, and he's not letting an NHL competitor in (or if it's his deal and he wants the option of moving the Ducks there)