Here are three features C1 does not have and could be supplied by the developer community IF C1 had the proper interface: (1) a raw level HDR merge, (2) focus stack merge, and (3) pixel-shift merge. Currently, C1 users have to process all the way to TIFF to do these, or worse, use other software to perform the merge from raw to TIFF thus forgoing the powerful C1 raw rendering capabilities.
You will note previous forum posts where developers have wanted to develop such a plugin (pixel-shift merge), but have been frustrated but the lack of the proper API.
As I understand it, the API will provide access to original RAW files - which doesn't help much as 3rd party developers won't have access to proprietary RAW format information, or the resources to develop for, such a wide range of files.
We need access to linearized RAW data; specifically, linearization, black subtraction, rescaling, and clipping, as described in Chapter 5 of the DNG standard. The plug-in could import this linearized raw data format, and then return data in the same format where the C1 processing chain takes over.
A 16-bit DNG file interface would be sufficient for pixel-shift and focus stack merge, but not for an HDR merge. For HDR, we'd want a 32-bit format like the HDR-DNG files that Lightroom produces. The last time I tried, C1 did not recognize these HDR-DNG files (although it does support the 16-bit linearized raw DNG). One would think that with 16-bit PhaseOne cameras, C1 would be developing some 32-bit processing capability. Why not define a C1 interface based on 32 bit IEEE floating point?