Something similar to this is already done for the cart reader firmware on mariko units on atmosphere to support returning from sleep on firmwares lower to that of the cart reader. The cart reader firmware is cached ( and I think it is also decrypted ) when not seen on a folder on the SD card. I think this cached version is the lowest you can go on the sysnand/emunand firmware without having the return from sleep issue.
This is a somewhat vague idea I have about it and I could be wrong/uncomplete, but the idea still applies.
AMS/Hekate dump and cache the warmboot firmware from package1 for sleep (mariko patched the warmboot bug, so we can't use a custom warmboot firmware like Erista), nothing related to the gamecard.
Dumping descrypted lotus firmware would require pwning the lotus, which nobody has publicly done or is interested in doing.
Older versions contains brick code. Not the latest (which is 3.1.0 i think?). But either way, you should switch to Atmosphere. This mess with patching games just sucks. Who wants to stay on firmware 11.0 all the time? Except for those people who believe that the sx os will magically get an update.
SXOS is dead. The website is down and has been down for a long time, and SXOS hasn't received any updates in nearly a year. You can't even buy an SXOS license anymore. SXOS is dead, move on to Atmosphere.
If you believe that SXOS is not dead, then you are delusional.