Installing new toilet

[Texas_diy]

I'm looking to get a bathroom added at my house in Texas. Slab foundation. Not interested in breaking it all up right now so a friend recommended installing it above the slab on a platform, and tying it into my laundry room drainage line just before it meets the main drain out the house. Can this be done? What are the cons of this? I haven't started this project just brainstorming and idea gathering now.

 

[johnjh2o]

Laundry drains are 2" you need 3" for a toilet.