Other than the Hoarding rule which applies to the corners of a robot's Alliance Home Zone, is there a rule that limits the number of Mobile Goals that a robot may possess?
No limit on Mobile Goals a robot may possess
There are no rules, other than SG7, which legislate how many Mobile Goals a Robot may Possess and/or Hoard.
However, due to the limited number of contested Mobile Goals on the field, Teams who choose to Possess and/or Hoard multiple Mobile Goals should expect vigorous interactions from opposing Robots. In most cases, these interactions will be considered "incidental".