There was hot debates about wether Moon exploration is to be achieved with manned crews or with unmanned robots. I think the mixed concept exposed here can use both, or be successful even with only one if the other fails.
First, only activities directly linked to lunar ground are useful on this ground: any other would require much less energy in free space. And things like telescopes are better in free space than fixed to a dusty and vibrating ground.
At first, a fixed crewed base on the Moon is useless: once the local geology explored, appears the need to move. (the only exception would be a large drilling project, which would require a fixed crewed base. But we are still far of this. And I don't speak of mining, a pure ideological view if we consider the cost of bringing back materials on Earth)
So we need to move. In order to be able to visit a significant number of targets.
A rover like Oppy and Spirit. But much larger, several tons like the LEM, see 20 or 30 tons.
There was on another thread on this forum (I don't remember where) an extensive discution about an automatic remote controlled Moon rover, its requirements and inconveniences. Large solar panels, which need to be cleaned. Full lab for isotope, cristallography and chemical analysis. Even gas analysis (rocks often contain gas bubbles very interesting to study). Such a lab could be miniaturized, but it would remain very complicated to operate and maintain, some said it would be even impossible to made it remote-controled and reliable enough.
Considering all this, I though of a mixed mission concept which would be interesting:
-a large automated rover
-several crewed missions using a smaller LEM to service it.
In remote control, the rover would be able to
-rove on large distances on the Moon (some even suggested to "race the sun" so that to alway have solar energy)
-take samples and make simple analysis.
Manned visits could:
-come on spots of special interest.
-take samples and manipulate them for more complete analysis.
-maintain the rover, bring new instruments or replace damaged parts.
-take back to Earth choosen samples of special interest for most complete analysis.
Concretely, the manned encounters could work that way:
-the manned landing module lands on a spot of interest, while the rover comes along to rendez-vous.
-the rover has a kind or skip or lorry, so that it can haul and carry the manned return stage. The crew can stay into this return stage, or have a larger cabin into the rover. From here they can perform EVA on the ground or for maintaining the rover.
-in this configuration, the rover can stay on the spot or proceed to other places, carying the return stage and the crew.
-when the human presence is no longer required, of if there is an accident, the return stage is fired and it goes directly to Earth (this is a bit more difficut than with the former LEMs, which had only to come back in lunar orbit).
One of the major advantage is that the manned visits don't need to bring each time an heavy luggage of rover, power resources and instruments: once landed, the rover can remain available for many missions.
So the whole thing works like the Hubble space telescope, most of the time in remote control, but with manned service missions. It just has more manned missions, and not just for maintainance. But the number of manned visits can be tailored according to needs and to budgets, from many to zero. Even in the later case the rover still has its interest.
The concept is even politics-friendly, allowing "ideological" manned presence to be really useful, and opposed conceptions (manned/unmanned) to collaborate rather than excluding each other. We can even imagine that he rover (US made, I guess...) could receive manned missions of Europe, Russia or other forms of collaborations.
It would not be interesting to rebuilt a series of the old Saturn V rockets, but I think it would not be difficult to rebuilt a series of a modernized version, using already existing components such as shuttle boosters, reservoirs or engines, together with modern electronics.
A nightmarish automation problem would be a complex automatized sample analysis lab able to stand the comparizon with a real Earth lab. Concretelly the belly of the rover would be organized around a handling "charriot" moving on rails, and able to carry samples from any instrument to any other (analysers, saws, containers...) with the proper orientation and force. The instruments would be mounted on racks, and there would be enough space for an astronaut to operate safely between the instruments, and eventually easily replace any of them, including the charriot. (rails being passive, could be considered reliable). The only real (but really bad) problem in there would be dust.