I have implemented it and it is very nice design I think.
It prevent to create dozen of column on the origin table because I guess an average installation may have about 2 or 3 different import format. For the CODA, I have already more than 10 field because I want the user has the maximum information when encoding the statement line.
Also it is nice feature that if you do not put a key, no value is shown so it is like having a invisible state setup by default.
I looks very similar to CODA.