You can indeed remove the multi-articulated torso to have room to add a computer, batteries and so on. Yet, please notice that the test we made with Raspberry Pi were quite bad:
The next version of Poppy will be released with on-board Odroid U3. The banana Pi can be an alternative, but it is just 2x raspberry, I don’t know if it will be enough to ensure good performances.
Also if I understand well, your are interested in the natural language communication between robotic agent and human. Maybe a first step could be to use only the upper body of Poppy so you can limit the cost and avoid the balancing problem ?