Can I retro-heat water from MF stove?

[dhaslam]

The heat exchanger would work better if  there were  flue pipes through the  boiler like  an  advanced steam engine. 

The pipes would need to be about 2"   to obtain sufficient  heat transfer but they could be quite close together.      Hard to make  but   could work well.  The bypass flap would need to be thermostatically controlled to allow the  stove to reach  full heat initially.