I have the download link for X3change (Author Arvo jaegel), but can't get in contact with him to ask for a fix for the new X3F file format
I correspond regularly with Arvo and, as far as I know, he has little interest in doing something for Merrill files which, IMHO, should be tagged .X3M or something. Arvo did some good work relevant to the SD9,10,14 and the early DP's. He posts regularly on the Sigma forum http://www.dpreview.com/forums/1027
as ArvoJ and might or might not be amenable to a PM from there.
As a longtime user of early Sigma DSLRs and sometime user of Adobe DNG Profile Editor, I would agree with the advice to make a TIFF from Sigma Photo Pro (SPP) and proceed from there with whatever tools are appropriate. For example, I could 'open as' a TIFF in ACR and then save as a DNG from there. I believe Adobe's DNG Converter also works on TIFFs and it certainly works on early X3Fs.
In ACR 5.4 and PSE, the only camera profile option for my X3F files is 'Embedded' and the drop-down does not change in spite of trying to put .dcp files in all sorts of places on my HD. Irritating, that. Enough to cause migration to RawTherapee for serious work (yeah, I know . . .)
Slightly OT, but SPP seems a bit generous in the saturation department: I find that -0.3 on the slider is more 'neutral' than zero sat.