Everything you said is absolut--- hah jk, :P it all makes sense lol. I am also dubious on them having three limited jobs each with interesting systems each being supported semi consistently (or other examples as you made, doesn't have to be "3 limited jobs"). And I think maybe you might see why I'm pushing for a duty finder option, in such case of the content drought for the side content. Although I also understand it's not "just that simple/easy" because of course as you said that means devoting forever to keeping Blue Mage balanced and up then.
But I really don't want to see Blue Mage die just because the side content isn't super popular or they have other side contents/limited jobs they want to do. So perhaps what I mean for blue mage and other jobs is:
- Create a system (like we see now for blue mage with spell acquisition) as a groundwork, perhaps add some fun side content for all players to enjoy (as we have for blue mage).
- Release it out and let people enjoy a fairly strong breadth of side content during the expansion drought (as they are).
- Then once the balls are rolling again make a strong beeline towards duty finder status for a few reasons. This doesn't mean dropping the side content but each blue mage update will have a strong bias towards adding the spells needed for duty finder, and increasing level cap.
First reason is that this way you can duty finder them sooner, rather than 4.5 blue mage introduced 6.1 blue mage duty finder its more like 4.5 introduced 5.2-.4 duty finder.
Second reason is that I agree that I don't think they can sustain many limited contents at once in a way that would satisfy players who like said content (if you love blue and want to see every patch have new blue content but now they're trying to also add puppet master and beast master, it's a bit harder). Or that it's not as popular so they just stop worrying about it. I would like to be clear and saying I'm not saying they can't update x because I'm their accountant or whatever lol and I would not be disappointed if they could do it all. If they can do it all then by all means do it because that's awesome!!! But that would make it seem money and time isn't a concern which wouldn't dissuade me from asking for blue duty then lol.
Third reason when you want to play blue mage and they can't keep the content pour strong (reason two based) you still have a whole job you can do regular new content. Content they will always ensure they work on (they can't just drop the normal content, that'd be a real riot). So even if they slow down on the side content blue mage still has the main content, blue mage like other jobs will never "die" then (I can absolutely see a limited job with no duty finder side die, because people didn't like it for whatever reason).
Now you may wonder what that would look like. So what I'd say is we start with a level cap of 50 right? During the drought we can add more spells but as we get to the expansion the number of spells focus down to what we'll need for duty finder (and the level cap increasing becomes a focus). They keep pushing that level cap till they've described the job in enough detail that they can release it to duty finder. If they can add more spells the better, the focus of development resources however is getting blue ready for the main stream. Such that say 5.1 they increase level cap add 2 spells, 5.2 again, 5.3 blue duty is finished with it's last two duty finder spells out. 5.3 patches on whatever interval on ward until level cap XYZ non-related to duty finder blue mage spells are released with occasional circus updates too (these spells can be from older content blue mage already level capped past).
Just so Blue Mages going back to old content don't rofl stomp a monster that has a new spell to learn they can give blue mages the ability to match their target in level (sync to target feature). "Mimic" spell or something.
So in a tl other words: I agree keeping many content drips going seems daunting (I'm not saying they can't), and I view allowing blue mage into current content as the perfect way to feed people who want blue while they sometimes are unable to keep the side content drip going (the people who /only/ want the side content will still get it as SE has time of course). But having the side content being a good drought breaker and side activity that isn't stressed too hard to update every patch. Such that you're not stuck with exclusively a dead side content job every few patches because the next Eureka took resources, then the next limited job, and oh you know what we decided all 2 of you who still play blue can wait.
Of course you could say "if they don't put work into duty finder side they can add more side content" but at least to me I think the likelyhood of blue being supported as side content 2 years from now with another limited job and all those systems (as you described) is low, while if they go into duty finder then long live blue mage.