Very nice model!!

As for rigging; you don't really have to use a skeleton if your model is made up of seperate pieces and you just want to do forwad Kenetics (FK). Looking at it, I'd say it is a bunch of seperate pieces. You could start by parenting the pieces to form a hierarchy. Example you could parent the foot to the lower leg, the lower leg to the upper leg, upper leg to the pelvic, the chest to the pelvic. Do the same to the parts of the arm then parent the upper arm to the chest... You get the idea. Now, all you have to do is reposition the center of rotation for each model part to the point that you want them to rotate on. Choose a model part then choose the translate tool then press INSERT. Insert lets you move the center point. After you move them all to where you want them turn INSERT off. After you do all that, you can rotate any joint you want and your robot will be posable...

If you want to use IK solvers with the model then you will have to use a skeleton.