I think if you more on macro, the 12-50mm macro port will give you more advantage.
I can't say how convenient for you, but I have no problem to rely on the Fn button. Most of the time at 50mm + wet lens and if needed you can switch to 12mm easily and flip the wet lens.
However, if I really want into macro - such as in Lembeh - I will use my 60mm.
If you have the OMD with 12-50mm and diopter at your hand, just assign Fn button and imagine you are diving in your fav. site and try to shoot any macro object at various sizes you expect you will see at the site.