Why can't Bosch Detail Sander be converted as an oscillating tool?
The sander ans accessories are designed for each other.  The sanding pads are special sizes for that sander.  

Not only are the accessories and sander made specifically for each other, but sander does not oscillate nearly fast enough for cutting.

If you pick up a dremmel multimax or milwuake multi-tool you will realize how fast they oscillate - you can hardly see that the bit is moving because it is so fast.

So I doubt that modding your sander to be a multi-tool would be dangerous - but I think that Bosch support was dead on: it wouldn't work.