I like it, very much infact, but there are some problems I can see.
First, the decal on the side is silvering. I dunno how to fix it with those dry transfers...
On the arms, on the joints, you didnt Aclad the insides of the circles on the outer part of the joint, on the forarms, and you can see bare plastic.
Those are the ones I notice right off the bat.
As to what this is. Its as you said, a Mobile Pod 'Ball' its a Space construction vehichle modified with a Cannon for combat (See militia/draft/using whatever you have avaliable)They were actuially quite weak and mainly cannon fodder
http://www.mahq.net/mecha/gundam/msgundam/rb-79.htm