"I have a script XXX, written as a module that can be inherited from."

Don't do that. Write a module and then write a simple script that accesses the module.

"If the grandparent's name changes, or the number of intervening parents to skip changes, code will need updating."

Which is why you should be using Roles instead of Inheritance, generally speaking. See Inheritance Versus Roles

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)