Difficult as in requiring more DeltaV and more radiation to deal with. But with beam or nuclear propulsion powerful enough to push the massive radiation shielding around that interplanetary flight already requires it becomes no more difficult than going to those other places.

I am a skeptic concerning both elevators and fusion. Near future? I am sorry but I do not think a space elevator is ever going to happen. It is one of those bizarro ideas that takes off for some reason but it is.….crazy. IMO.
As for fusion, the only two places fusion will ever work as advertised is in a star or a bomb. IMO
Beam propulsion, on the other hand, has the potential to allow cheap lift and is the “only technology” that will make it happen.

The second major leap must focus on what we do once we can economically and efficiently move mass to orbit. Entrepreneurial firms such as Planetary Resources, Inc., that are developing plans to mine the near earth asteroids will need ample energy resources, both in the form of delta-V propulsion requirements, (rocket fuel) and in the mining and refining of the valuable materials they will retrieve from the NEOs. The propulsion delta-V requirements can be derived from the NEOs, in the form of water or hydrogen and oxygen for propulsion if they have sufficient refining power available. Therefore, the second major hurdle that must be developed is high energy density power sources in space. There are really only two viable options to provide multi-megawatt power supplies in space within the next 50 years; these are large solar array collectors and compact fission power plants. There is no new technology necessary to develop for either of these options, but there is still substantial research needed for manufacturing and deploying large solar arrays in a zero gravity environment. In addition, large solar arrays are not easily moved and therefore to be of maximum utility, the ability to beam power from the point of generation to the point of use will need to be included with the development of large solar arrays. Therefore, the logical short term solution to opening up space resource development is compact nuclear fission power plants. Compact fission power plants in the multi-megawatt range are already developed and can provide the power necessary for refining low grade ore from the NEOs to high value materials for use in Earth’s industries, and in producing fuels and breathing atmosphere for in-space mining activities from water ice contained in the NEOs. The third major paradigm shift that is necessary for colonization of the moon is further development of beamed power technology. As efficient and practical as compact nuclear fission power plants are, they are still costly and require sophisticated management and operational protocols for their safe operation. Compact fission power plants in space can provide the power necessary for manufacturing and deployment of large solar arrays in Earth or Lunar orbit, but it is not a chicken or egg situation; refining, manufacturing and deployment of large solar arrays requires the initial availability of compact high energy density source of a nuclear power plant. Similarly, a viable lunar, Mercury or Asteroid based colony must have ample power available to produce water, breathing atmosphere and building materials from source materials that are similar to igneous rocks on earth. This is only practical with ample power supplies, not limited by a 28 lunar day-night cycle. But where does beamed power enter into this picture? The initial colonization of the moon can be carried out without geographic constraints if compact nuclear power plants are used initially as the source of power. However, orbiting large solar arrays in lunar orbit with beamed power to the lunar surface can be the transition technology between lunar surface-based compact nuclear fission power plants and helium-3 fusion technology. The promise of Helium-3 fusion power from Helium-3 deposits on the moon or Mercury is an integral goal for a self-sustaining lunar colony (Schmitt, H., 2007). A careful economic analysis (Beike, D. 2012 in press) indicates that with minor improvements in space transportation systems, export of Helium-3 from the moon to Earth represents a viable business that could easily support permanent lunar colonies. The economics may not be that different for Mercury. However, the deployment of beamed energy technology would also allow high density power generation on the lunar surface, and this power beamed to lunar or earth orbit to support entities such as Planetary Resources in their asteroid mining ventures could be a viable economic benefit to lunar entrepreneurs, linking the economic development of the Earth, Near Earth Asteroids and the Lunar surface in an expanding triangle trade association that would be beneficial to all.

By the time we are able to industrialize Mercury, we might be able to have automated balloon-based mining of the atmospheres of the outer planets where mining is easier and (I believe) He-3 is in much greater concentration (albeit the gravity wells are greater).

I understand that Mercury’s magnetic field is overwhelmed by the sun’s wind.

Still, a resource-plentiful platform for solar power seems very attractive.