Thanks to all for a fun and engaging thread.
One idea that hasn't been floated yet, but which I believe deserves consideration, is a 10m or 15m transmitter aboard bbSat. Years before actually being able to communicate through an amateur satellite, I listened to the RS robots on 10m and 15m, and that achievement gave me the confidence to proceed. I therefore think a transponder that downlinked on these bands would be likely to 'broaden our base', and it would help keep active these, now unused, satellite bands.
I recognize that transmitting on such a long wavelength from a 10cm cube represents a technical challenge, but it would largely be a challenge of mechanical engineering, not something that would run up against the limited power budget. I also vaguely have the impression that amplifiers, etc. are more efficient in the lower frequencies, so that might be a plus. (Not to mention reduced path loss.) Perhaps the effective power out would be so low that a directional antenna would be required on the ground. In which case, I'd say it was a no-go, since that would preclude too many of the new experimenters that we'd be hoping to snare on these bands.