There is a specific definition of MINIBOT, including the parts it must be made out of. It does not have to meet the size/weight requirements for the ROBOT; it has it's own set of rules. See section 4.3.14 of the manual for rules on the MINIBOT and section 1.6 for definitions.
There is currently a debate about whether it is permissible to launch a passive MINIBOT to hit the target, which will hopefully be resolved in a Team Update or Q&A response within a couple of days.