The pipes are now buried under concrete and fill. There is finished structure all around them. It’s not new construction where it’s easy to set pipe and make changes or replacements.
If your house main needs replacement it is a major, major job that requires a backhoe to dig a trench from your house to the sewer lateral. To expose it, and either replace the whole line or at least make the repair to the existing line. Replacing a main costs 8-10 grand.
Inside the house repairs are dirty, intensive and expensive.
Seems to me you don't make that mistake twice.
Access panels from now on.
If the bathrooms are broken, then put some bathroom trailers out front for people to use. I remember using one of these last year at a Home Depot that was having the bathrooms upgraded. The trailer bathrooms were nice and even had AC.