The system menu files of system menu's with versions below 4.3 are confirmed to be offline.
The sad sad news is in the title folks. Confirmed by testing with NUSD and ModMii.
Since several IOS's are down, and those are used as bases for cIOS's, we can't build cIOS's with ModMii or other tools.
Sources: Myself, and ModMii Support Topic.
On a side note , ninty is now hosting partys in my pants