Smaller is probably better. I read something in Forbes (or maybe Fortune Small Business) about a guy who is building small rockets capable of launching things like science experiments and people's ashes into space. He's apparently one of the first clients of Spaceport America.
I don't think they were capable of deploying satellites or additional stages, but perhaps a similar design could.
Another thing to consider would be having the planetary transmitter be a separate module from the rover, allowing a smaller rover, and a smaller lander. The rover would then just need a less powerful radio. The more powerful transmitter could be landed separately, or even remain in orbit.
I don't think they were capable of deploying satellites or additional stages, but perhaps a similar design could.
Another thing to consider would be having the planetary transmitter be a separate module from the rover, allowing a smaller rover, and a smaller lander. The rover would then just need a less powerful radio. The more powerful transmitter could be landed separately, or even remain in orbit.