user McSusanin suggested that flashing the 1206 rom and keeping the kernel to 1114 solves or at least improve the battery drain / deep sleep problem.
However I cannot replicate what McSusanin did: I flashed the 1114 rom (sp flash tool, selected everything, download only), then I flashed the 1206 rom (sp flash tool, selected everything except lk, download only).
However in the info the kernel is that of 06/12.
I also tried to flash back 1114 rom (only lk and lk2), flashing ok, but nothing changed in the info.
Note that this is testing only and if you want to flash you are responsible for what you are doing: take into account that you can brick your mobile.