Fuel depot at L2

Over at the Bad Astronomy and Universe today forum, I saw a thread about going to Mars.  I'm doubtful about a Mars mission.  Someone mentioned in flight refueling and how that makes a Mars mission plausible even with smaller rockets.  Well, that is interesting.

The idea is to put a fuel depot at the L2 Lagrangian point (on the far side of the moon away from Earth).  This is called the gateway to the solar system.  It would also give you easy access to Geo orbit as well as lunar orbit.

I wonder how the big ET tank could fit into this?  Would it be in the way, or could that idea be integrated into this somehow?  Could you get that big tank all the way out there?  Or would it be better in lunar orbit?  A big station would seem useful for manufacturing facilities as well as help in getting to and from the lunar surface.  You could use this as well as the L2 depot, it would seem.

Now if you refill this depot from lunar water, how interesting would that be?  Or you could refill from NEO's.  That might be even better.

Update:

It would be easier to get the ET to L1 instead.  Leave the fuel depot there, and then take the ET to lunar orbit.  Use a tethering system to get back and forth from the lunar surface.  If the ET is in polar orbit, that would make it more accessible to water in permanently shaded craters.  Mine the lunar water from these craters and take them back to the ET.  Launch from the ET to get back to L1 fuel depot.  Now:  is this all feasible, or is it a fantasy?

Tethers have been tested in Earth orbit with not much success from my impression.  But in a lunar gravity field, maybe they would work better?  Perhaps, perhaps not.  You could wait until carbon nanotubes become more available, and then hope that will work.  Or perhaps conventional materials would work now.  I just don't know.

Now some of my reading on rotovators suggest that one of these could fling payloads out with plenty of velocity.  But would you want to use it?  And what would be the drawbacks of using one of these setups?

Update:

I did some comparisons with the Apollo program and the Shuttle program.  My calculation may not be correct, but I think that the ET can get to L1, maybe even to lunar orbit.

Now, that doesn't mean it is capable of doing this, but it may be possible at least in theory to do it.