It will be much more profitable than mining ?
Considering current difficulty of PoW mining - absolutely.
There are lots of miners with GPU farms becoming useless due to increasing difficulty (even for altcoins mining). Sometimes mining profit doesn't even cover the cost of electricity spent for PoW.
Fog computing projects using miners' computing resources for calculations give the new life to solo mining.
What do you mean saying 'even for altcoin mining'? Of course you utilize only the hardware used for altcoin mining! For Bitcoin nothing except the most powerful ASIC's make sense to use for many years now. But you are not able to use those ASICs, right? Your expression above is misleading.
Anyway, I wanted to ask which GPU are you planning to be able to use? What are smallest specs to be able to mine for SONM? Which version of cuda, opencl, how much ram? Sure I don't expect exact numbers, but just an idea on the min specs... For example, will Radeon 280x do? 380x? And what about HD5770 or similar?