Ohh, it's been a while since I did something with this, and now just today I when I played with it again I suddenly realized what's been the problem all the time!

I feel a bit embarassed even, the solution is so simple

The problem I had, was that I used incorrect way of shutting down the watchdog when I did the kexec() to the 2nd level kernel! Now why did I ever make such a novice mistake

Well, I can happily report now that I can reliably boot at least Harmattan, Nemo and Nitdroid fully up from multiboot touch menu, without being anywhere near a computer