I'm thinking of maybe downgrading my o3DS, and using whatever games I have on hand to update to various firmwares and make NAND dumps to get pointers for more firmware versions, unless someone beats me to it. There are only 7 more payloads to add to support every firmware from 4.0-9.2 (or 6 if I skip 4.0 and go with 4.1-9.2),
I have games with updates for at least a few of those versions. I want to get a copy of Cubic Ninja first though so that I can actually test my work. Adding support for the rest of the firmware versions is easy, but time consuming. At least support for 6.x and 7.x would be useful. 5.x isn't particularly useful since users on those firmwares could just downgrade without really losing any functionality.
I have at least a couple 6.x and 7.x games.
Tested this and it worked fine on my N3DS running 9.0.0.
That's good news. I expect it to work fine on other versions too then. I haven't been able to test it because I haven't gotten ahold of a copy of Cubic Ninja yet, but I was reasonably sure it would work. I had double and triple checked the modifications before posting.