Happy New Year. 

You are right that there is currently not a simple mechanism for calling feff from larch.  Of course, on could make a system call, but that's not specifically about using feff.  It should be fairly straightforward to write a function (or class) to generate a feff.inp file and call the feff executable.  As far as I know, no one has done this.  If you're interested, that would be a great addition!  I'd be happy to help anyway I can.

My expectation had been that most people would be using larch from Artemis, but that hasn't happened, yet.  I have been focusing much of my efforts in the past year or so on beamline and microprobe software, and less on EXAFS analysis.  But, improving the interaction with Feff is an important need for larch, and would be really useful.

We have sort of "Grand Plans" for this, using the recently released Feff8.5-for-EXAFS (see http://github.com/xraypy/feff85exafs) to make a more interactive, and callable version of Feff, so that one might create a set of Potentials, then build scattering paths (and calculate the EXAFS for them) dynamically.  Bruce has been working on this quite a bit over the past several months.  For this, the eventual plan is to get rid of much of the "Control Card" aspect of feff.inp, and instead make functions (for C/Fortran/Perl/Python/larch) to do things like
    CalculatePotentials(list_of_atoms, ...)

and
    GenerateEXAFS(potenials_data, scattering_path)

I don't think we have a definite time-line for that, and it is probably many months away.  But, I think that an effort to generate and call Feff6 or Feff8 would be great, and could easily be modified / extended to use this next generation of Feff-for-EXAFS.

Neither Bruce nor I do this development full-time, and we'd love help on any aspect of this work. 

Cheers,

--Matt