GUI for ofono could be easily written
but what exactly you mean by "break sound elsewhere"? Break it at all, or only during call?
In case of future projects that would recreategui for phone, addressboo (or using some existing project?), and sms database (mms code could be borrowed from FMMS on maemo)
this project could become what deblet failed to be - a full featured alternative system (without sacrificing phone functionality) for N900.
I suspect, that power-saving bits may be harder than phone things. IIRC, it was first major issue to overcome for Mer. I wonder if things of interest for disabling-disabling hardware parts may be found in their source code? Maemo's idle power consumption (with offline mode, screen locked etc) is as low as 3-4 mA per hour. Quite a challenge to replicate it.