raised exit of soil stack

We are thinking of moving our bathroom from upstairs to downstairs in our flat.

The problem is that the downstairs outlet for the soil stack is at about 30cm above floor level. The soil stack then exits and continues down through a neighbouring apartment.
For various reasons we cannot have a raised toilet (ceiling quite low) and we don't like the noise etc of a sani-flo pump.
Is it possible to move the exit of the soil stack down to floor level (assuming we can get our neighbour's permission to knock down and rebuild part of the joint wall and to join back into our joint stack lower down?)
Is this a pretty specialised plumbing job?
Very very grateful for advice!!

if the stack is in a party wall you may find that both your outlets are opposite in a cross IE +

Thanks for your advice. I guess the only way to find out is to get someone in to have a look at how excactly we connect to the neighbours