@Keeptoiletssafe
First, the researcher's scientifically proven solution to "fecal plumes" was not to install gapped doors or move sinks outside. It was simply that hospital toilets should have lids, which should be closed before you flush.
Your claim about door handles being the primary disease vector is challenged by the article, which states that floors and high surfaces yielded higher levels of aerobic bacteria and fungi than hand-touch sites.
The researcher theorized this is likely because hand-touch sites are cleaned more thoroughly than other surfaces.
Second, the study stated that every type of toilet in the three hospitals received the same cleaning every day.
If a universal toilet gets twice the foot traffic (because it is available to 100% of the population) but receives the exact same cleaning frequency as a segregated one, it will logically be dirtier. That is a management and scheduling failure, not a structural design flaw.
For your architectural points:
Door damage from mop water:
Modern commercial and universal cubicles use solid-grade laminate or phenolic resins, not porous domestic wood.
They do not expand or jam. Furthermore, you do not need a 12-inch visual gap to drain a floor.
A standard undercut of a few millimeters is standard for airflow and drainage while maintaining privacy.
Occupancy and fire doors:
Commercial universal doors use vacant/engaged indicator deadbolts.
You don't need a door to rest open to know it's empty.
Ventilation:
Mechanical extraction (HVAC) is already a mandatory building control regulation for commercial bathrooms without windows, regardless of whether the stalls have gaps or not.
Lastly, this design is cheaper to build by combining the separate work needing to be done on two separate rooms into one (like combining the plumbing) and the technology pays itself back over time.