You are really trying to do something you do not have the experience to do.
1. If it were even possible to have one tank for two toilets, it would need to be double the water capacity because BOTH toilets would have to flush at the same time.
2. Taking the vent off the side of a tee and then having the wall hung toilet flush past it would violate every code and principle of plumbing.
3. I do not remember ever seeing a baffled closet tee, other than with a So-Vent system. The closet tee you are referring to is the way to flush one toilet past others on a lower level, but it usually means the lower one will be offset about 5" from the centerline of the stack. I have never seen or worked on an actual Gerberit wall hung, but most of them have the tank in the wall so your pipes would have to offset around it.