Thanks everyone for the comments!
About allowing a paramater: Not sure how much this is useful here, since this memory manager acts entirely in the background of the engine. Its true that the developer of the component is responsible for registering it and thus creating the pool, so I could allow it as a parameter, but since all this does is allocate components that are being used by the ECS exclusively, I don't think it makes sense her, but thanks for the pointer anyway (will need to think about more general memory management strategies at some point).
What should you actually choose for alignment? 4 byte, power of two, 16 byte?
For a memory manager, provide alignment as a parameter with a default that matches the build settings.
As it has been publicly released, you might look over the EASTL implementation. Note how they provide a method with default alignment, another accepting a parameter for custom alignment and custom offsets for arrays.