Send the Homebrew formula upstream
In theory, this just means submitting the formula upstream as described at https://docs.brew.sh/How-To-Open-a-Homebrew-Pull-Request#formulae-related-pull-request
In practice, the formula is currently unacceptable because it uses Meson's wrap system to download and install dependencies, including Xgandalf, PinkIndexer and libccp4. Our current formula explicitly removes --wrap-mode=nofallback
from the Meson arguments to allow this to work. While we could contribute a formula that doesn't do this, it's very likely that we'd immediately get complaints about the lack of at least Xgandalf.
The only way to make the formula acceptable would be to create separate Homebrew formulae for Xgandalf, PinkIndexer, LibCCP4c, FDIP and Millepede. That wouldn't be too difficult in principle, but it would be a lot of work to get it all up and running at first.
An alternative would be to contribute the formulae to Brewsci/bio, which already has a libccp4 package (pulled from cctbx/ccp4io, which I think would work with CrystFEL).
A final alternative would be to create our own Homebrew "tap".