I think Pyke is near-obsolete, at best static with no development since 2010 as fas as I can tell
This is a bit worrying, to say the least.

We could replace it with another Python logic programming solution, but they all seem in a similar state IMHO (check it out).

Instead, I reckon that the actual rules operation is really quite simple and not hard to rewrite in ordinary Python. Which would certainly make the rules easier to maintain.

BTW, I don't think we are really making ideal usage of the logic programming concept in the loader anyway : A rules-type language would be a really good solution to assigning netcdf variables to specific CF categories. This is currently handled by the iris.fileformats.cf wher the CfReader using the identify methods in the various subclasses of CFVariable.
Either that is a missed opportunity or, possibly, it just shows that pure Python solutions are actually perfectly adequate !