Yes it should not be a problem to have downloads of deleted worlds available for your own personal enjoyment.
One option was to remove all worlds and just have the existing Permanent with mining on the same map but in a far off location. That takes away the need to update every plugin on every separate map as each separate map is in fact a separate server, it takes time and even more when updates go wrong, plugins break, stop being developed etc. It's not just a case of hit update and all worlds update.
I started Hangouts quite a few years ago with one map, then moved onto using a plugin for multiworlds but it wasn't reliable, things broke, all worlds shared the same mob cap etc, it wasn't the best experience for multiple players online at the same time. My daughter was a baby then, she slept a lot as she got older she needs more of my attention. Steve came along with his much more vast skills with servers etc. and this is where we are at today. I don't do an awful lot now, it's easier for one person with the skills but it takes time, Steve doesn't have the same amount of time he used to have, life and work change over the years. It costs more in money and time.
Less maps = less time updating and fixing. Spigot/paper/waterfall actually get updates very frequently, sometimes every few days. These updates can fix and also break things.
Permanent as has been said caters for the more casual slower/less play time player but players with more time on there hands can still play on there. I actually half moved to permanent but sometimes I have the time to play but don't, something is not giving me the draw to play but I always like the first few weeks/months of a reset. I've even played on the Vanilla server but got to a point were the draw to play diminished after a while.
Seasonal with less perks and a bit harder gives me a bit of an eagerness to play if I get fed up it will eventually reset again and I can start over. I don't think I'm the only one who feels the same. Resets of maps always brings in a lot more players and slowly people stop playing again, they get a bit bored. Reset happens and more people are back for a while.
We can't please everyone all of the time. I can see both sides of the map setup argument but we are trying to find the middle ground.
(It must have taken me an hour to write this, with child and wife interruptions.)