From my point of view, within this specific case, these two design strategies go hand in hand. It is hard to give this a good place within the bicycle lamp design since this is a fast moving consumable (at the moment). For upgrading, adapting, disassembling and reassembling, the user needs a form of attachment to the product that motivates him or her to take action. This won’t be the case for something as disposable as a bicycle lamp, at least not at the user side. When a fast moving consumable moves back to the company, the value needs to be restored.
Every form of effort that is needed to dis-and reassemble the product, will be expensive. Especially since this bicycle lamp is a low-segment product that needs to be cheap for the consumer. On the other hand, if the product is too easy to disassemble the user is exposed the fragile parts (LED, PCD, battery and connections to create a closed circuit). When a company maintains ownership over a product, it is important to give all the separate parts the longest lifespan possible. This way, all these different parts can be used in different product over and over again. There is a tension field between the company manufacturing side and the material and component conservation side.
A possibility is to create a connection in which the housing is closed which the user cannot open at all without specialized tools (that only the company owns for example). The downside of this is that the user will not be able at all to open the product, so if there is in any case a user that has an intrinsic motivation to repair, this will not be possible. On the other side, it will be very easy to make a very good waterproof connection that protects all the different components creating a longer lifespan for the product.
Whenever the product is broken or a part has reached the End-of-Life, the user should be able to return the bicycle lamp. When the lamp has reached the company again, is should be easy to open with a custom made disassembly tool and easy to identify the error. When all the different parts are separable without damaging, these can have a second life within another product, creating value for the company over and over again.