Have you considering including a function that reads raw (some are now ".xlsx" files) gas exchange files and "cleans" them up a bit? Functionality could include:
1) Read in .xlsx or .csv files as directly output from the gas exchange units including all the header lines, etc.
2) Remove header lines, lines with units, etc.
3) Read in a full directory of such files, rbind them together, and automatically create an ID column (for use with fitacis) based on file name or some other user-defined sequence/columns
4) Remove blatantly poor data (e.g. negative Ci, etc.)
5) Print an output that says something like the following, which would tie directly into any additional documentation of varnames.
"These are the variable input columns that you have available to use as model inputs:
RH: "RH_S", "RH_R", "RHsfc"
CO2: "CO_S", "CO2_R"
I might have some old code that could help with this I could dig up if it were helpful.