2.) Spoofing is at the top of my list. It would make it easier to play dumped game carts, and more importantly would allow local play with Switches of a later firmware version without risking an accidental system update offline. With Spoofing, it won't matter to me if Nintendo comes out with a 6.3 that breaks things again because I would still play with others and could download game updates from friend's Switches without updating the firmware. Then I could afford to be a few versions behind everyone all the time and be totally fine.
1.) I personally prefer XCI over NSP, because while the NSP gets installed to the microSD card, the XCI can be moved elsewhere to save space. I have no problems dumping game carts to XCI and I have no interest in converting an XCI to an NSP, but I would love to be able to convert my purchased eShop games and/or DLC to an XCI. For that matter, I would love to have an option to select any installed game and after creating an XCI from it, to then removed the installed NSP files to just use it as an XCI game.
5.) I use Checkpoint for save game backup, although it could still be improved. For example, there doesn't appear to be any good way of accessing the saved games on the sysNAND. If I wanted to get a saved game off the sysNAND, I would have to take the Switch offline then make a NAND dump then run CFW on sysNAND then run checkpoint and then restore NAND and then go back online. If I wanted to get a saved game onto the sysNAND there doesn't appear to be any way without risking an immediate ban.
It would be nice if SX OS had a feature that would allow me to import saved games from the sysNAND for a particular title, and an option to resign it for another user. It could also have a feature to inject the save back into sysNAND. There should be no ban risk of importing a save, and very little ban risk injecting a save to sysNAND.
...
I also like the idea of custom themes, but higher on my list would be an option to run a NAND dump as if it was emuNAND for the purposes of booting into OFW without any option for homebrew or backups in that mode, which would exist to play online. So we just never touch the sysNAND for anything and play online in one emuNAND and use homebrew and backups in a different emuNAND. The best of both worlds, without having to burn fuses or see vulnerabilities close.