Unusual data point (I'm not sure if South African practice is applicable elsewhere) , but most bigger corps I've worked at have provided a mechanism to declare

Unusual data point (I'm not sure if South African practice is applicable elsewhere) , but most bigger corps I've worked at have provided a mechanism to declare external interests, pending management approval, to work around these global clauses. On paper any IP would be default belong to the Corp, but after some discussion/negotiations with your line manager and his higher-ups, you could do the paper work to declare.