In general it is very difficult to change structural type of stuff like moving a toilet in a condo. It is simply not the same as doing work in a single family residential home. Beyond it probably being difficult to alter the plumbing in the building for such a change, it is unlikely that you would get permission from the HOA.

The roof of the parking structure below is most probably not just a slab the way it might be in a single family home. It would have pipes and electrical wiring since there are no doubt lights in the parking structure and there might be pipes and other structural stuff there.

The condo board is not going to sign off on something like this without have something that assures them it can be done without compromising the building. And even if that was possible, obtaining that would be very expensive and I doubt would be worth it just so that you don't see a toilet in a bathroom. Bathrooms HAVE toilets - no surprise.

A shower drain is different than a bath drain - even one in a tub/shower combo. I live in a condo (FWIW) and when I remodeled I converted the tub/shower to a walk in shower and the drain had to be changed. I needed to access it from my neighbor's bathroom - luckily he gave me permission. The condo HOA needed to approve the change as well but this modification is much less difficult than moving the location of a toilet - especially in a multi-family residence. There are 122 units in my building - all of them have been remodeled since the building was first constructed and not a singe toilet has ever been moved.

I would think he was referring to reinforcing steel in the slab. It's possible, however there will be disturbance to the unit below. Even changing the 1-1/2" line to 2" will require tearing through the ceiling below. An engineer who has the original plans for the condo may be able to tell without seeing it in person but you would have to give him/her the exact location proposed.

Can the door into the bathroom be moved so the toilet isn’t the first thing you see?

Not a pro here by any means but would it be feasible or allowable to turn toilet to one side or other, of course keeping toilet flange in same spot, may not even need to turn but to build a potty closet with saloon doors or something of that sort, and shortening that vanity at the back wall to allow space for such?

Can you include a sketch of the floor plan that exists with measurements & location of existing fixtures?

Thanks you for the comments.

June Know: Yea, I thought he was probably referring post tension, or really thick concrete bc the parking is underneath them. Are you saying a shower could go in the back corner, utilizing the same 1.5" drain, if no more than a 2.5 gpm fixture is installed? If so that solves that problem bc they are going to have a 3-way diverter and 2 fixtures (showerhead and hand held). I'll find out the gmp rules for their area.

Sharon: Yes the door can move along the same wall that it is on, but not the sides.

Alice: I'm waiting for the exact measurements of the bathroom. It doesn't look big enough to me for a toilet room, but since I don't have the measurements, I can't say.