I'm wondering if you really need that level of resolution for IR photography. I think your a7r is likely fine. The other main issue, as mentioned above, is lenses and potential hot spots. On the Sony and others, these are known, but on the Hasselblad, it is possible that you can't find a lens that will perform. Risky, but someone was the first jump out of a perfectly good airplane.
Joel
I imagine Hasselblad will come out with a true X1D successor at some point that I'd upgrade to (the mkII has a nice set of improvements but not worth the upgrade for me at this point), and that's the time when I'd consider converting the X1D - after upgrade when the X1D is sitting around as a backup cam. Potential lenses issues are definitely a concern and not sure I'd want to be the guinea pig for XCD lenses and testing third party lenses via adapters.
Assuming everything goes technically fine with disassembly, replacing the cover glass, and reassembly, worst case scenario with a full-spectrum conversion is you just shoot with a "hot mirror" (UV/IR filter) on the lens and it
should perform as it would non-converted (or just convert it back).
The A7R was a little odd. Sometimes the results were great, sometimes they weren't. It's hard to explain. The biggest issue for me with the Sony's is that I found I just don't like using them that much. I also had an A7RII (not coverted), and the menu system and user experience was not my favorite, although they did deliver what I needed image-wise. I've since sold both the A7R-FS and A7RII. Not sure I see myself getting another Sony, but I need another 35mm FF system at some point in the near future so who knows. Really wish they'd work on their menu system.....maybe it's improved with the III and IV series.