Without seeing the location, I would venture to guess that, if money were no object, it could be done. In construction, we like to say, all things are possible, some things just take more time and money. Options could include making a wider wall for the inwall tank, and provide space for the bends. The bends could be placed perhaps under the floor. If it's important, they may be a way found.
Check these links below for more info, you will have to do a copy and paste into the address bar to go to them. Terry
: A rear outlet toilet and a wall hung toilet can be two different items if the rear outlet one sets on the floor. But if it is a wall hung system, then it needs a carrier fitting and that normally is straight into the stack. The thing that can require an elbow is if the tank is directly behind the bowl and cannot be offset, then the stack behind the center of the bowl would interfere with the tank and the unit would have to be set off to the side of the stack using an elbow.
: : I am renovating my bathroom and need to use a rear discharge toilet. We are located on the second floor of a three floor building and must exit into an existing wastepipe.
: : We purchased a Duravit wall-hung rear exit toilet with a concealed tank. When it arrived, our plumber said it wouldn't work because there was no installation room for the waste elbow. The manufacturer said the exiting elbow must make a 90 degree turn before exiting into the wastepipe. We can't do that and must go straight back into the existing wastepipe. Any suggestions?
: : Help please!