To pin a bolster on correctly, you would but a small chamfer in the bolster and then pound the pin to form a rivet. I can't picture a way of doing that without ruining the look of the mosaic pin. If the bolster was epoxied or soldered on, then the mosaic pin could help with shear force but not holding-it-together-force. If it was epoxied on, the mosaic pin could make the construction stronger, especially if you cut grooves in the pin for epoxy to fill, but not as strong as riveting a pin. If you're going to solder it on, you'd have to epoxy the pin in afterwards because soldering temps would melt the epoxy that makes up the (usually) black insides of the mosaic pin.
I'm sure it would work, but it's up to you to decide if it's tough enough. People consider it strong enough for scales so I don't see why not. I think most people don't rivet their pins anyway and if they do, they grind off the head when shaping the handle. It's an interesting idea. I've done it on jewelry but that doesn't need to stand up to any forces at all.