How would one plumb two bathrooms from one rough-in?
You are &quot;f'ing&quot; crazy if you think that raising part of your floor is easier than doing some very very minor concrete work.   There are all these gotchas for raising a floor and then finishing it so it doesn't look ghetto.
Now for doing it right there is breaking concrete, creating a bed for pipe, laying pipe, backfilling, and then adding in quickmix concrete.   It is 8 hours of work.   You will spend days trying to figure out how to put a toilet on an elevated box that looks OK.
Just do it right.   The elevated floors should be a last case emergency thing.   I have finished hmmmmm maybe 50+ basements never have I raised the floor to tie into the stack.
Also from a DIYer perspective, when you are breaking the concrete and filling... there is nothing anyone can see.   You can mess something up or have a half assed finish and no one sees it.   You raise floors and every carpentry thing sticks out like a sore thumb, every edge, every finish.    You may be scared to break the sledgehammer out on the floor but in reality you are creating 5-10 times the work for yourself AND IT WILL LOOK WORSE EVEN IF YOU FINISH IT GOOD.
Note:  The hardest part of breaking up a basement floor is carrying buckets of concrete out (assume 20) and disposing them.   Everything else is really easy.  I did want to mention this because it is a workout.