LED lights, including landing lights, are the way of the future. I have test flown them on several aircraft types, including an EC120 helicopter, in which it was fantastic. I just installed two large LED lights on our Fire Department ice resuce airboat, and was very impressed. There's an LED landing light in the near future of my C150.
Though one could seek an "approval" (STC), being a person who provides such approvals through the Transport Canada system, I can tell you that I have argued LED bulb installations down to not be "major", and thus not requiring formal STC or similar approval. Referencing the Canadian criteria for what constitutes a major mod (requires STC), an LED bulb placement does not come close, and is minor. As such, it can be accomplished with "specified" data, AC43.13 for example. This becomes a discussion between the aircraft owner and maintainer, but it is a discussion well worth having.
I doubt that the regulatory authority would have an interest in driving such a simple and worthwhile improvement to require an STC, it just ties up the approval system with zero value added work. Though I do not know the ins and outs of EASA's system, I would be pleased to see more of these replacement/improvement mods getting easily accomplished. If an owner or maintainer is struggling with an LED replacement modification, please tell us here, perhaps this is a place where pulling together, can help set some worthwhile precedent.