Replacing the Prolog engine by a proof assistant. These systems delivers proofs of propositions in a theory. By using a theory supporting a kind of word problems and forcing the problem author to express the problem as a a valid theorem in this theory would have the benefit of uncover hidden assumptions on the problem statement.
Also, these systems being more expressive than Prolog clauses, and supporting complex tactics for automatic proving could benefit the maintenance of the system.
On the student side, the discovering of new facts is converting into asserting propositions that can be transparently proved by tactics or presented to the student to deal with them: This would lead to re-using the same problem in different educations levels according to what is assumed and what is proved by the student.