Not a bad idea per se. I wonder though how the micro-tools perform in real life, especially in terms of leverage and getting into hard-to-reach places with the weirdly shaped bits and bracelet frame.
This seems strictly a (very) light duty tool. Good for small repairs, maybe electronics, gadgets etc. I like multitools for what they are, but even a full-sized Leatherman has issues dealing with stuck screws, tightly fastened bolts and the like.
BTW, I agree strongly that a modular approach to multitools would make life easier for many of us. It's one of the reasons why I'm not that fond of the famed SAK - I could never really find the perfect combination of tools for my needs so my SAKs spend most of their time in the drawer sadly.
It is possible to modify many modern multitools, though. Most of the larger Leathermans can be disassembled if you can get hold of the necessary driver bit (which looks something like a weird torx head). With some effort it is possible to replace the existing tools with something else. I've done that on my LM Wave and a buddy of mine did a similar job on his Skeletool. Unfortunately, it does require more skill and equipment than the average DIY projects and may not be worth the trouble in the end.