Okay, there's a few issues here.
First, the installers are correct, as far as the OTARD rule is concerned. If the dish in any way extends beyond your exclusive use area, then your landlord is within their rights to refuse to allow the install.
It is also within the landlord's right to deny drilling holes to run the cable in. So how do you plan on bringing in the cables from the outside? Flatwire is not the best option, and most DirecTV techs try to avoid using it due to failure rates and chargeback service calls associated with it.
As to your mounting option of a pot with cement, let's think about this. First of all, you will need a two inch OD pipe for the dish to mount to. Now this dish about about 36 inches across, and can develop wind loading of around 60 psi. Do you really think a pot with some cement in it will keep the dish standing upright? No way will a DirecTV tech worth his salt touch that one, since he's just setting himself up for a chargeback.
You may be able to get a tripod designed for the Ka/Ku dish, or even a non-penetrating roof mount for the dish to be mounted to, but these are not part of the standard install so you should be prepared to pay extra for those. Also, depending upon where they are located on your balcony, your landlord may be able to declare them a safety hazard because they could impede your exiting via the balcony in an emergency.
And now we come to the biggest headache with apartment installs, aside from landlords. Grounding the dish. The NEC has some pretty specific requirements for the grounding of the dish, and it is almost always impossible to comply with it on an apartment install.
