It's going to be cool to get user-replaceable batteries back in new phone releases. Depending how it goes I can see myself keeping a spare instead of a powerbank
Powerbank: Works with all phones, Doesn't require you to shut down and take your phone apart, Can be charged with a regular phone charger.
Spare battery: ???
The whole discussion on what the EU is doing has devolved into this idea that everyone will be forced to offer a backplate that pops out and a battery you can remove with your fingers.
The directive is far more complicated, and you will not see that at all.