As for a more complex data transmission scheme, do all satellite receivers support it?
Provide a simple feedback form or voting system. It doesn't have to be perfect, these downloads are already hand assembled by someone each day. You aren't obligated to use all suggestions, or even the most popular, but use it as a feedback mechanism to inform your choices.
How about using that nifty Tor browser they keep rebroadcasting to access a hidden service website to vote and issue requests? Hidden services cannot by definition be accessed without Tor and are thus more secure from prying eyes, even when used by non-technical users.
> As for a more complex data transmission scheme, do all satellite receivers support it?
The satellite receivers just store the transport stream. The data is extracted by parsing the transport stream with a Windows program. You can implement whatever scheme you like with software.
Even if the above makes the voting easy to rig, it's more important to ensure anonymity than perfectly accurate voting results. And even with biased voting data you can figure out what the users are interested in. If nothing else it will help you cull content, as lack of interest is also a good indicator.