Arthur, that is how all crossettes are made essentially, whether or not they're color changing.
I actually had a special pump made to make these. It's just an ordinary round hole crossette pump with a second depth stop hole drilled in it to allow me to essentially make donut shaped comets. It's drilled such that the cavity part of the crossette almost touches the pressing surface.
Pressing two drastically different compositions together and expecting them to stay together is probably not going to work very well. If it did, making tipped comets or color changing comets would be trivial and be done all the time. The different drying rates of different compositions often makes the two compositions separate or weaken. These have to be pasted anyway, so it probably wouldn't be a big deal. I'd just personally prefer to make the two parts separately, and then glue them together with a little BP/NC slurry and paste them.