PLAN copying / rotating fleet of DARPA ACTUV (ASW Continuous Trail Unmanned Vessel). Park them outside sub home ports (outside of territorial waters / contiguous zone but within active sonar range) and blast sonar to keep continuous track once they're underway. Likely then hand off to faster/more powerful surface ASW platforms. Combine with rumored mini nuke boats from PLAN, especially if autonomous improves to drastically reduce manning (less mouths to feed to match endurance of big nuke boats), basically tailgate nuke boats the second they leave parking lot. Trumpet following girl meme. Economically, hard to say, but only fraction of very expensive to operate 14 boomers/SSNs on deterrent patrol at any given time.
That said, IMO hardly matters, sea/air leg of triad can be replaced by redundant / distributed land, not silos but road mobile TELs in hardened shelters probably for MUCH cheaper per warhead - PLA/PLARF model. Can have 1000s of cheap TEL trucks / fake warheads to play shell game and be just as impossible to decapitation strike as a few SSNs with 20 missiles. Mobile land leg just politically not sensible because it means unambigiously painting target on homeland, not just empty silo fields in bumfuck nowhere. IMO half the reason of sea/air leg now is they're out of sight/out of mind doing distant patrols. No one wants to see a nuclear TEL driving down the highway and process implications. If anti missile defense improves, cost/benefit of limited magazine SSNs gets even worse - a tube on a 2.5B+ nuke boat cost 100m to acquire + likely very expensive operation costs per shot to field. You can buy 500+ HEMTT 8x8 to hull around solid fuel ICBMs for that price. PRC can probably buy 1,000. Economics of nuke boats as delivery platforms outside of psychology does not seem to make sense, but civilian psychology when it comes to nuclear planning is very important.