The thing is, zeppelins have the thing where a lot of their flight characteristics aren't nearly as tightly tied to their bomb load as a heavier than air craft. You could very feasibly loft a hundred thousand pound bomb load across... five, six ships, and have a seventh along to air-launch a stripped down Hurricanes with trapeze rigs as close air defence. Not much compared to a flight of Lancasters, until you realize you can operate out of some forsaken aerodrome in the Midlands, and they're completely capable of executing circuitous missions and time delay raids in areas thought to be untouchable. They're also very good at nebulous location strikes- Tirpitz would last a month at most before a theoretical airship bomber squadron obliterated her.The desire for the Bomber Command types to pull them away is also very real, but the fact that these fly very slowly in comparison to most bombers makes them less "sexy" and attractive to the Bomber Harris type people. There's also a fairly disastrous PoD there, though, when all of this was in position and they did misuse them for bomber support, as you suggest they might.
Loitering and ultra-long duration is quite literally the traits that make them such good submarine hunters- but now you can apply it to turning Kiev into a firebombed hellscape via the expident route of overflying Sweden and Norway and coming in from the north in the Baltic where there's a weak air defense network instead of coming in over the heart of Germany. It's not a straight case of everything a fixed-wing can do, an airship can do better, but in use certain use cases the marginal problems of airships can be negated. Strategic bombing and marine patrol are the two big ones- and everywhere else, airships suck. Take them anywhere within ten miles of a furball, for example, and you'll have Me110s crawling down their throat and murdering them unless they're porcupine nests of Bofors- and then there goes your payload weight!Huh.
Ultra-long-duration / loitering bombing missions.
I hadn't thought of that.
Regarding submarine aircraft carriers:4 - The other side would have evolved attempts to stop them. I think that ASW would have been the hardest to stop (outside of submarine aircraft carriers? Could that even be remotely possible); anti-airship airships would run into aeroplane screen issues (only for ultra-long-range vs ultra-long-range options, but that's still a very evocative idea). You'd probably see redeployment of air defence networks to protect the heartlands that were previously out of range - but that has knock-on effects that they are no longer deployed as per OTL (there's a limit to resources, after all...)
5 - Airship production would be ramped up considerably due to 1,2,3 (and part of 4). This leaves a whole bunch more airships by the end of the war and new roles being searched for.
I went with that option in WIAF, the tycoon in question being Song Ziwen a.k.a. T.V. Soong, one of the richest men in China, who OTL was the brother-in-law of Sun Yat-sen and Jiang Jieshi. He orders two airships from Goodyear Zeppelin in the late 1920s with the intention of starting his own international transport company, only to have one crash in 1932 and the other one be commandeered by the Chinese military at the start of the Sino-Japanese War. The latter shows up in @Bruno's story "The Road to Yakutia" featured in the book. In the end Song's involvement in airships fails to make a difference in the greater scheme of things.But the early 20th Century also had a considerable number of rich individuals (maybe not quite as noticeable as the tycoons of the 19th century), but if one such had caught the airship bug, it is possible they could have either been more popular at the time of the PoDs above, or even stubbornly remained plying the air lanes.