Regarding the capture of the beamed power, coliminated, or "maser" technology is already a somewhat mature technology, as microwave radio transmission towers have been around for at least 20 years. Admittedly, hitting a 3 meter dish at 70 miles is somewhat different from hitting from martian geosynchronous orbit (10600+ miles). This would still require a rectenna roughly a kilometer across for high-intensity microwave transmissions. Lower powered transmissions would require larger collectors, up to 10 km along the major axis, depending on the latitude of the receiving station. The smaller axis length is due to the fact that Martian geosync satellites orbit at about 2/3 the altitude of Earth geosync sats. Martian atmosphere is essentially transparent to EM radiation from ~.1 to 1 meter wavelength. Power transmission is based on amplitude and frequency. However, you start running into CO2 absorption at the higher freq end of this spectrum. The rectenna would require a grid of wires spaced at 2 * wavelength intervals. So, yes, a fair bit of empty space. Since these wire are fairly thin (1-2 cm apiece) they could be mounted on poles above the colony if the lower-powered option was chosen. Since the rectenna could reasonably be expected to pull 5+ GW of power, it might be possible to subdivide the rectenna with proper diode alignment so that each hab has its own draw from the overall rectenna. This would, in turn, raise all sorts alternate missions to service said rectenna. To note, though, this would be a MAJOR undertaking to emplace the poles and string the wires / wire bundles. Definately not something a newly established colony would have immediately available.
Edit:
Gah, just noticed a major error: the grid spacing would be 1/2 wavelength, not 2 * wavelength. Stupid mistake.